The Largest Ruby in the World

The 125West Ruby is one of the world's largest known ruby crystal weighing in at 8.2lbs and amounting to 18,696 Carats. The Ruby crystal is semi-translucent to opaque and contains rutile. If cut en cabochon, this may create a six ray star. When exposed to long-wave ultraviolet light, the ruby displays a strong red fluorescence. It measures 122.4mm x 112.3mm x 133.9mm.

If you have doubts, this gem is certified by the Gemology Institute of America Report 15171991 dated May 24th, 2006. If carved this Ruby would be the largest ruby curvature in the world. If cut en cabochon, the 125West Ruby would be the largest cut and polished ruby gemstone in the world.

Rubies have a long history within the mechanism of a watch.
 In 1702, Nicolas Fatio (Facio) de Duillier, a Swiss mathematician who was born in Basel, Switzerland, and Pierre and Jacob Debaufre introduced Jewel Bearings into a  watch movement to reduce friction; however, the jewels were not widely used until the middle of the 19th century. Until the 20th Century these jewels were ground from tiny pieces of natural gems. The watches had garnet and quartz, but it was the luxury top quality watches that used sapphire, ruby and even diamonds.

In 1902, a process to grow artificial sapphire crystals was invented, thereby making the jewels cheaper. In most modern watches, synthetic rubies (left image) are used between the moving parts, especially in the escapement and have a major effect on the timekeeping accuracy. It was discovered the harder the material used as bearings, the lessor the friction. Thus the ultra hard slick surface has a lower coefficient of friction with metal. In addition Rubies increase the life of the bearings. Rubies is the second hardest material after diamond and seven times harder than topaz. The Ruby belongs to the Coronado group of minerals, its name stemming from the red color (Latin: Rubeus). Red corundum is always called by the name Ruby whereas any other colors of corundum are known as Sapphires. The only difference between synthetic sapphire and ruby is as a result of the different impurities that have been added to change the color. There is absolutely no difference in their properties as bearings. Rubies can be opaque, translucent or transparent.

The very best watches have a 21 jewel movement; some have slightly more and some less. Some ETA movements use a 25 jewel movement which is a question of style rather than functionality.

Water Resistance 101

It’s over 90 degrees  outside and its time to head to the beach, but what about the watch you are wearing, can it handle a dip in the water? Well it all depends on water resistance of your watch. Before we get started, I must make one thing clear.  There is no such thing as a “water proof” watch.  That term was discarded years ago.  Now watch manufacturers prefer the term “water resistant“, although I must say the Hublot King Power 4000 meter diver comes pretty close to having optimal water resistancy.   Hublot’s Diving Watch can Dive to Depths no man has dived before!
Watches have varying degrees of Water Resistance depending on the efficiency of the gaskets (O-rings made of rubber, nylon or Teflon, which seals the watch where crystal, case back, and crown meet the watch case); quality of sealant as well as the thickness and material of watch case.  A screw in case back and crown also increases water resistance.
When buying a Water Resistant Timepiece take note of the water resistance to see whether it matches your lifestyle.  Below is a water resistance  guideline:

• To describe a watch as water resistant or 2 ATM, it must have a minimum of 20 meters water resistance; however it is advisable at this minimum requirement, water should be entirely avoided.

• 30m or 50m (3 to 5ATM): Minor Splashes.  Okay for fishing and hanging out by the pool. You can wear the watch in the rain, provided it is not a torrential down pour, and you can wash your hands under a faucet.   NOT for swimming and diving.  Many Haute Joillerie watches encrusted with gems are water resistant to 30 or 50 meters.

• 100 meters or 10 ATM, is suitable for swimming and pool diving, but not for serious sea diving or sports where the water pressure can become quite high like in white water rafting or waterfall plunging. 

• At 200 meter  (20 ATM) water resistance, you can do some serious marine sports and competitive swimming and diving from a diving board; however, if the watch is not specifically designed for diving, one should check on whether one can scuba dive with the watch.

• Divers 200m to 300m (20ATM to 30ATM), one can dive with scuba equipment not requiring a Helium Tank.

• Divers 300m + Helium Valve.  Here you are getting into some serious deep water and a Helium Valve ensures the watch will not be damaged as a result of the tiny Helium molecules which sneaked into the watch case while under the water.  The Helium Valve releases these molecules and reduces the pressure within the watch. The helium and hydrogen molecules cause no damage while the watch is at great depths under pressure but as soon as the diver resurfaces, a pressure difference occurs between the trapped gas(es) inside the watch case and the surrounding air. This can cause the crystal to pop off damaging the watch thus the helium valve is a crucial edition to diving watches enabling the diver to release the gas build up and restore equilibrium.

TAKE NOTE:
Although, a watch may be labeled as having a specific water resistancy, the water resistancy can lesson over time as a result of gasket deterioration, especially if the watch has been exposed to salt water or chlorine.  In order to maintain the water resitancy of the watch, it is advisable to get your watch serviced at least once every two years.

Mother's Day Sale Until May 7th at ZULUTIMEZONE

"A printed card means nothing except that you are too lazy to write to the woman who has done more for you than anyone in the world. And candy! You take a box to Mother—and then eat most of it yourself. A pretty sentiment!"Anne Jarvis - the creator of Mother's Day. (depicted in image)

On May 14th 1907, Anne Jarvis held a memorial for her mother who had died two years earlier. She then embarked on a mission to make Mother's Day a recognized holiday which occurred in 1914 ,thanks to Woodrow Wilson who signed the bill. She did not like the commercialization of the holiday and spent her entire inheritance fighting against it. She did not like the cheap cards and empty trinkets associated with the holiday. She wanted the holiday to be full of meaning, depth and gratitude.

No one could have said it better then Anne Jarvis,  the creator of Mother's Day herself, but then again she never saw the stunning woman's watches at ZULUTIMEZONE.COM, for if she had she would have approved. Approved very well.

Perusing through ZULUTIMEZONE.COM website, I couldn't help but notice how many gorgeous woman's watches are on sale until May 7th, 2012.

NFW Milan Watch Model 04807

The NFW Milan watch ,with a vibrant deep red metallic sunray dial and exquisite tonneau shaped case, caught my eye.
The bezel is punctuated with 8 screws providing a sense of elegant efficiency - perfect for a mom who gets things done and makes things work.
  The bold red face adds more than just a hint of adventure - a vivid backdrop for discernible chrome markers.

Although this watch exudes a bold "make way for mom" presence, the watch only weighs 3 oz and is a mere 9.5mm thick.  Since we know mom's time is precious and punctual, the NFW Milan is powered by an efficient and precision Miyota Quartz Movement.
The  34mm long x 24mm wide case  is crafted from the ultimate and most popular in watch material - Impact forged, Surgical-Grade 316L Stainless steel.  This is the same steel used by all the top watch companies.  In fact many companies who predominantly made  watches out of gold are now using 36L stainless steel instead.

 And if adventure takes mom into a dark place, whether it is the Darien Gap or the dark gap between the shed and the garage -to retrieve a lost baseball perhaps, dial hands coated in Superluminova will "glow-in-the-dark" and display the time. The dial is protected by a curved and hardened mineral crystal adding increasing its scratch resistance. 
  And if mom finds herself in an area where the overhead sun shines with a bright intensity, mom can read the dial - no problem - due to an anti-reflective crystal treatment.

NFW Milan Watch Model 04087

Mom won't have to remove the NFW Milan while splashing through streams or washing a dish or two, since this watch is water resistant to 165 feet.



The NFW Milan Timepiece is presented with a choice of two attachments.  You simply can't go wrong here. No need to angst over  mom's desire for a bracelet or leather strap - this watch is presented with both.  It is up to mom whether she wants to wear an  elegant stainless steel bracelet or a super comfy Italian leather sporting a stylish croco pattern.  Switching between bracelet and strap is quick  thanks to an easy change spring bars.

This is an excellent everyday watch with "not an everyday" markdown.  For this Mother's Day, ZULUTIMEZONE and dramatically reduced its prices on some of its best ladies watches.  The NFW Milan has been reduced from its everyday low price of $179.00 to the "Mother's Day Special" of $145.00.

I could go on and on gushing over the tremendous variety of woman's watches available at ZULUTIMEZONE.COM, but I would spoil the fun for you. Go ahead ENTER ZULUTIMEZONE.COM, and purchase a gift for Mom  for Mother's Day. She deserves the watch and you deserve ZULUTIMEZONE.COM's low prices.

Let me know what mom says...

101 on Watch Winders

Croton Imperial Dual Time Zone $229.00

At Zulutimezone many of the watches are powered by automatic winding like the handsome Croton Imperial Automatic.  
To keep the watch running one may need a watch winder.

What is a Watch Winder?

A Watch Winder is a device specifically designed for Automatic Watches.  The Watch Winder winds the watch when off the wrist.
Automatic Watches, invented by Perrelet in the 1770's,  are wound by the swinging motion of the wearers arm. This is achieved by a semicircular 'rotor', an eccentric weight that turns on a pivot, visible at the back of  the watch. The swinging motion of the wearer causes the rotor to swing back-and-forth on its staff. The staff is attached to a ratcheted winding mechanism. The motion of the wearer's arm is transferred into the circular motion of the rotor and via a series of reverser and reducing gears, winds the mainspring providing power to the watch.
 Modern Automatic watches contain two ratchets and wind the mainspring during both clockwise and counterclockwise rotor motions.

.  When the watch is not worn, the rotor does not move and although the watch keeps working for a certain period of time - depending on its power reserve capability - the power depletes and the watch eventually stops. (Most automatic watches have a power reserve of 48 or 72 hours. Some watches even have a 7 day power reserve like the IWC Portuguese Automatic, but those watches are few and far between.)
To avoid the watch stopping, it can be placed in a watch winder.  The watch winder mimics the swinging motion of the watch, rotating the rotor and thereby providing power to the watch  and preventing a lapse in timekeeping.
In addition the watch winder usually provides the watch with additional protection from dust and moisture.  Some watch winders even double up as a Safe. 

I have a battery-operated Quartz Watch. Do I need a Watch Winder?
 No. The Watch Winder has been specifically designed for the Automatic Watch; however the Watch Winder works for "batteryless" Quartz Watches for example the Omega-matic,  Seiko Kinetic and other innovative watches. These watches use the same weight/rotor principle to generate electric power to  the quartz movement.

I have a manual wind mechanical watch. Can I purchase a Watch Winder too?
Manual wind watches do not have an oscillating weight usually because the company wants to maintain a slimness not  possible with a rotor, or if an intricate movement may be masked by the rotor.  These watches require manual winding at the crown.

 Most Watch Winders are specifically designed for mechanical Watches, and up until a decade ago no Watch Winders were available for Manual Wound Luxury Watches; however in Basel 2000, the company Orbita unveiled a Watch Winder for Manual Wound Watches. Utilizing small collets that grasp the crown of the watch, the Orbita Sempre Winder winds the Watch just like you would wind it with your fingers.


I own one Automatic Watch. Do I need a Watch Winder? Probably not. If  own only one Automatic Watch, and wear it fairly often, then chances are you do not need a Watch Winder.   If you almost never wear the watch in question, wind it up every couple of weeks and then let it run down; however, if you have an Automatic Watch you wear quite frequently but not continuously, and you usually have no time to keep resetting the time, then the Watch Winder may be a worthy investment.

I am an avid Automatic Watch Collector. Do I need a Watch Winder?I would have to say yes, unless of course you desire to walk around with multiple watches on each arm. In addition many watch winders are equipped to wind many watches at the same time and double up as a showcase.
Many watches equipped with complications such as a moon phase indicator or perpetual calender (a complex complication that accounts for the differing lengths of months and leap years) need more intense time, date and day/ night adjustments if stopped. 


Is it true that the oils can coagulate and clog the watch movements once the watch has stopped?

No! Most oils used today are less viscous than earlier oils, and thus are not prone to coagulation.




Can I purchase just any Watch Winder?


No. There are many Watch Winders out there, some are quite cheap as in the $100 range; however beware of gimmicks. Not all watch winders are of equal quality. A cheap watch winder may actually harm the movement of a watch with jerky motions. A luxury watch requires a good watch winder with smooth regular motions.

What is an example of a good watch winder?

The Italian Made Scatola Del Tempo Rotori, is an example of a good watch winder. The Watch Winder is capable of winding multiple watches at once depending on the model. The watch winder rotates clockwise and counter clockwise switching direction automatically. The case is aesthetically appealing with a warm Briarroot Wood Exterior and Leather and Jacquard Silk Interior. In addition, the Watch Winder can double as a Watch and Jewelry Storage Case capable of storing Strap Watch, Rings, Cuff links and Bracelets.


For avid watch collectors who like to make good use of their space can purchase a Bergamo 40 by Orbito equipped with a
watch winder module on command. The watch winder unit slides into oblivion transferring this watch






Why are Watch Winders quite expensive?
As I was shopping around for Watch Winders, I realized that for a simple rotating Watch holder, the prices range from anywhere between $200 and $8000.Aside from the companies emphasis on quality, precision and exceptional luxury watch care, a Watch Winder is an item that is produced in limited quantities. It is a specialty item that does not have sufficient demand to be mass produced.
Watch Winders are becoming more popular as the automatic mechanical trend is rising.

Does the Number of Watch Jewels in a Movement Make a Difference?

 In the 1950's, The Waltham Watch Company of Waltham, Mass introduced a 100 jewel watch. Only 17 of the jewels were functional meaning those 17 jewel were placed between the gears of the watch to reduce friction, hold lubricant longer, reduce the amount of lubricant needed, increase temperature stability and reduce corrosion. (All reasons jewels are used in movements today).

 There were two cap jewels, two pivot jewels, an impulse jewel for the balance wheel, two pivot jewels, two pallet jewels for the pallet fork, and two pivot jewels each for the escape, fourth, third and center wheels. The remaining 83 jewels were simply placed at the edge of the automatic rotor (seen above). These jewels had absolutely no function and so created the watch with the most amount of non-functional jewels. Although there is a space for a 101th jewel on the automatic rotor, the space is vacant as 101 jewels does not sound as marketable as 100 jewels.
The Walthman Watch Company closed its doors in 1957 as a result of financial stress and less than perfect craftsmanship, it seems the 100 Jewel Watch was its last desperate attempt to make a sale. The company relied on the fact that many people believed the more jewels the more precise the watch movement. People may have believed the jewels were actually worth something.

In fact most jewels are synthetic costing very little and the jewels themselves are worth very little.

In the 1940's and 1950's many companies were upping there non-functional jewel count without increasing the complications. Between 1902 and 1965 it was "anything goes" in regard to the amount of jewels in a watch movement. In addition the amount of jewels were stated on the dial as a marketing ploy. Then in October 1965, the Swiss organization NIHS - Normes de I'industrie Horlogre Suisse, whose function was to develop the standards for the Swiss Watch Industry, published a standard (NIHS 94-10) in order to control the way in which the number of jewels in a movement are used in advertising and any sales related to horology and timekeepers. In 1974, the NIHS and ISO 1112 which was recently updated in ISO 1112:2009 specifies the technical definitions of functional and non-functional horological movement jewels. In addition it describes the different types of jewels used, and how this is to be marked on a timekeeping instrument or used in advertising. In this way the type of jewels used, the amount of jewels used and the way in which the jewels can be used to increase the jewel count of the watch is outlined.

De Grisigono Otturatore DL 19-89 Movement

Today the more jewels indicate more complications as there are more moving parts. The more jewels used, the less the wear and tear on the watch parts. Many watch companies use 21 jewels and some ETA movements use 25 jewels. The jewels themselves are valued at very little since most are synthetic; however, it is the well placed functionality in conjunction with superior craftsmanship of the watch part that attract watch enthusiasts and horology admirers.

Watch Maintenance 101

A new watch when purchased is in optimal condition and with correct maintenance can remain that way for years to come.  A watch can be crafted by the most prestigious watch company, but if not taken care of can run into ruin. I have listed a couple of good tips to keep the watch you just purchased from ZULUTIMEZONE.COM in tip top shape:

1) The Watch Crystal - Glass Covering and Protecting the Dial

There are three main types of materials used in covering and protecting the dial.

Offshore Limited Commando Black-Red Chronograph

•  Acrylic - Inexpensive plastic prone to scratches, but  shallow scratches easily buffed out. Acrylic is used on kids watches and low range fashion watches.
•  Mineral Crystal - a type of glass, oftentimes heat treated to further harden the surface and increase scratch resistance. Mineral Crystal is relatively cheap and keeps the overall cost of the watch down.  Even hardened mineral crystal are prone to scratches and therefor the precautions ,listed below, must be taken. Mineral crystal is the most widely used crystal on the OFFSHORE LIMITED BRAND found exclusively at ZULUTIMEZONE.COM
• Sapphire crystal is a transparent form of synthetic corundum , used in high mid range and high range watches. Sapphire crystal is an extremely hard substance: Three times harder than mineral crystal -  9 on the Mohs Scale - silver being 2.5 and a diamond being 10,  thus Sapphire Crystal is scratch resistant but not Scratch Proof. In addition if struck with a sharp blow at a certain angle, sapphire crystal can shatter. Learn more about Sapphire Crystal

 To avoid any type of scratches or damages to your watch crystal follow these guidelines:

a) Wrap your watch in a soft cloth before placing it on a hard surface.

b) When not wearing place your watch in its original box. Do not place your watch in a jewelry box with your other jewelry. Keep in mind diamonds have a Moh of 10, harder than sapphire crystal and thus can scratch the watch.

c) Do not wear your watch with other jewelry on the same hand. For the same reasons listed above.

d) Avoid wearing the watch during high risk activities like rock climbing or bob sledding unless of course you own a watch specifically designed for these type of activities.

e) Avoid scraping your watch against corridor walls or on furniture. Some new man made materials used to make simulated stone surfaces contain incorporated silicon carbide, an extremely hard material that can cause damage to your sapphire crystal.

Even though many watch companies like Seiko and Invicta have developed signature watch crystals claiming exceptional hardness, the above precautions still apply. 

2) Watch Bracelet and Strap Maintenance

a) Metal bracelets should be carefully washed in water. If the bracelet is really grimy use a soft new toothbrush dunked in mild soapy water and gently brush away the dirt. Rinse with water (if your watch is not water resistance be careful to use only a minimal amount of water and do not get the case wet). Dry carefully with a soft cloth. Cases should be wiped gently with a slightly moistened soft cloth and carefully dried.

b) In hot weather, leather straps should be slightly loosened to prevent perspiration absorption. There are two reasons for this: Firstly a tight strap prevents the passage of air flow on the underside of the strap and secondly a tight strap may cause a perspiration rash on the wrist. When your watch becomes wet with perspiration, wipe it dry with a soft cloth. In addition, leather straps may begin to smell from bacteria trapped in the leather - Click here to read a Summer Caution for Leather Strap Watch Wearers.  

c) Finally when taking off your watch leave it in a well ventilated area. Never place it in a sealed air tight container when the watch is still damp with perspiration. Never leave your watch in direct sunlight this may cause your watch strap to fade.

Movement Maintenance - Either Quartz or Mechanical (Automatic or Hand Wound) - Click here to learn more about the definition of a mechanical watch movement.

Automatic mechanical watches:

Gold Piaget Rotor

 These Watches do not require manual winding, but are powered by the gentle swinging motion of ones arm.  This swinging motion moves a rotor or oscillating weight affixed to the back of the watch. The rotor transfers power to wind the mainspring. Thus in order for the watch to keep ticking, one needs to wear the watch everyday or ever second day depending on the power reserve of the watch. (Power reserve is the amount of time a watch can operate without winding).
Take note even though a automatic watch is powered by the natural swinging motion of ones hand, the watch should not need to be shaken vigorously like a cocktail. In addition, avoid undue shocks like dropping the watch on hard surfaces like a granite kitchen counter. Avoid wearing a mechanical watch while playing golf or tennis as arm speeds in excess of 70mph can damage the movement of the watch. Vigorous jagged motions can damage the movement. Many watches have undergone stringent testing and are Certified Chronometers, but still proper care is still necessary.

Listed Below are Maintenance 101 for Automatic Watch Movements:

 a)  If one has not worn the watch in a couple of days and not kept it on a Watch Winder, the watch

b) A Mechanical Watch requires servicing just like an automobile. Although mechanical watches are designed to provide a lifetime of accurate and reliable service, a mechanical watch requires servicing  every three or four years.  This time frame will ensure maximum efficiency and  prevent permanent damage. Every manufacturer has their own specific servicing recommendations for your watch. As a result of the complexity of the mechanisms within the mechanical watch, it is preferable the watch is serviced by an agent authorized by the watch manufacturer. During servicing your watch will be inspected for worn parts which require replacing; checked to see if  lubrication is required, and examined to determine if perspiration, dust or water has seeped into the watch. Dust and water is the most damaging to the watch movement and removal of these elements are crucial.

c) During servicing your watch is opened and the movement removed. If required the movement is taken apart to the very last screw. Each individual part is inspected for wear or tear. Old worn parts are replaced with identical parts. Every part is cleaned, reassembled and lubricated. Then the movement is regulated, so the watch will run with precision. If the watch is water resistant, water tightness is checked and worn cracked gaskets are replaced. The final step is polishing the case and the bracelet. After these steps the watch will be good as new.
d) Quartz Watches require a battery change once every one to two years. If the back of the watch is a snap back type, one can use a blunt knife to remove the cover and change the battery; however, if the watch is the screw back type (noticable by usually 6 equally spaced slots), one may require a special tool to remove the back. Click here for an excellent article on tips for changing your watch battery.

Take Note: Servicing is crucial as the oil that keeps the watch running breaks down over time. Parts of the watch that are no longer lubricated will cause friction. The problem will be confounded if the friction creates microscopic fine dust that will act as a damaging abrasive to the movement. In addition, the watch case expands in response to periods of hot and cold. This expansion allows dust to enter the case to microscopic fine cracks. Dust is the most detrimental element to the movement of a watch.

I know what you are thinking. This seems like an awful lot of instructions for a watch; however, most of it you are probably doing anyway. Please bare in mind if you treat your watch with respect it will be your great grand child's heirloom.

If you have any other tips or personnel experiences. Please feel free to comment. I love feedback.

The Power Behind a Mechanical Timepiece

• A mechanical watch has one source of power - YOU! What powers you? Coffee perhaps? You may have just rolled out of bed, rubbed your eyes and fumbled for your watch. If the watch is manual wind, you wind it without much thought, but you unleash a series of remarkable actions performed by numerous components housed within the watch case.

The majority of mechanical watches, like the STØLÅS Mens Harbormaster Genoa Swiss Automatic Diver Watch, available at ZULUTIMEZONE,  are automatic and wound by the swinging motion of ones arm thereby setting an oscillating weight ,at the back of the watch, in motion.

The oscillating weight or rotor in an automatic watch or the crown in a manual watch winds the mainspring - the power source in mechanical watches. The mainspring is a spiral spring of metal ribbon coiled around an arbor (the central axle); the inner end of the mainspring is attached to the arbor with small hooks or tabs, and the outer end to the barrel ( a cylindrical box).
The mainspring is wound by turning the arbor, but drives the watch movement by the barrel. This ensures that the watch is still being powered during winding. A ratchet with a click mechanism  is attached to the arbor so  the force of the spring will not turn the wind the arbor. Once the arbor is wound it no longer moves. The pull of the stored energy of the mainspring turns the barrel. The barrel has a ring of gear teeth around it. The ring of teeth interlocks with the center wheel pinion and drives the wheel train. In most watches the barrel rotates once every eight hours, thus the 40 hour spring needs five turns to fully unwind.


Some useful facts pertaining to the mainspring of your Mechanical Watch.

• The Mainspring is wound around the arbor with great force. Disassembling the mainspring without the "know how" could cause the mainspring to suddenly release, causing injury. The mainspring should be 'let down' gently first by holding the winding knob and pulling the click back. This allows the spring to unwind slowly. In general ,the disassembling of any luxury watch, should be done by a watch professional.
• Older watches, such as those made before the 1960, had mainsprings that broke quite frequently. This was due to the constant stress cycles endured by the metal, causing the metal to weaken and then snap. The stress was the strongest directly around the arbor, where there was no space between the coils, this point could quite easily be reached, while winding. Although, metallurgy has improved, broken mainsprings although rare can occur.
  
• Some watches will no longer work when fully wound. This led to many theories of over winding. Over winding is a myth and does not validate the reason for fully wound watches to stop. Winding a watch all the way, does not damage the watch; however, over time the watch movements collect dust and the oil dries up. The dust and oil causes enough friction so the smooth running of the mainspring is hampered, leaving little force for the mainspring to turn until the end of its running period. If the owner continues to wind the watch, without servicing the watch, the friction reaches the flat part of the torque curve and the watch will stop, even though the watch is fully wound.
• Mainsprings can become tired or deformed, and lose some of there force. This will cause the running time between winding to be decreased. At this point your watch needs to be serviced, and your mainspring replaced if necessary.
  
• Power reserve indicator: Some watches are equipped with an aperture on the dial indicating the amount of power left in the mainspring.  To achieve this, a differential gear is required to determine how far the arbor has been turned compared to the barrel.