1967 Longines Ultra-Chron Caliber 431

Longines Cal 431 Front

This Longines Ultra-Chron Caliber 431 was a labor of love (which is to say it took an incredibly long time and was more expensive than I had imagined.) The finished product is a wondrous movement famous for its rare and rapid tick.

Once again I got more than I bargained for with buying a watch “As Is” but that is the nature of this work. That being said, I did not expect to see so much damage inflicted upon such a beautiful piece. A perfect storm of sloppy work, laziness, and incorrect parts substituted for proper ones necessitated the tracking down of several major and mostly obsolete parts to get this running properly.  It required new balance jewels, shocks, a new main plate and a whole new calendar mechanism.

Listening to a high-frequency watch is an experience in horology like none other. If a regular watch beat is like a human heart at rest, a high-frequency movement is a human heart after a 400-meter dash. The odd thing is that both accomplish the exact same goal of unwinding a mainspring at a fixed rate so as to make the calculation of time possible. A high-frequency movement is just working about twice as hard to be just a touch more accurate (in theory.)

The base rate that a watch beats at is 18,000 vibrations per hour (vph.) This means that the watch’s balance completes half of an oscillation 18,000 times per hour or 5 times per second.  The theory behind higher rates is that more beats per second means less rate variation in different positions experienced during daily wear. At the time that the Ultra-Chron was introduced, high-beat watches were at 28,800vph. Then in 1966 Girard Perregaux came out with a watch that beat at 36,000vph or twice as fast as the standard 18,000vph. Longines soon followed in 1967 to mark their 100-year anniversary with their line of Ultra-Chron movements, which also beat at the astonishingly fast 36,000vph.

Such a high beat requires some changes to the gear train. The balance wheel is noticeably smaller than a common one and the escape wheel has 21 teeth instead of the standard 15. Other than those two modifications however the mechanics are identical to any other watch. Additionally, the 36,000vph movements incur additional wear and present more lubrication issues than lower vibration rates. For this reason, the 28,800vph is now much more common among high precision calibers and the 36,000vph movements are seen as a short-lived example of “extreme engineering” in horology.

During their nine years of production Longines produced several caliber variations as well as a near infinite combination of case, dial, and hand designs from the very standard to the more trendy of the time (this piece clearly fits in with the latter.) As can be seen in the ad below, this watch originally came with a mesh metal band, but that was long gone by the time I got my hands on it. Personally I prefer it on leather.

After an exhausting restoration, I am happy to have this beautiful piece done, ticking, and sitting pretty in the “finished” pile.

Longines Cal 431 Feature Longines Cal 431 Angled Longines Cal 431 Side Longines Cal 431 Movement UChronAd3

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