My wife's Geneve Dynamic has altitude sickness@

maybe it got magnitized?

Certainly not altitude related. Probably magnetized somehow.

Sounds like a warranty job to me. Has the shop that serviced it done good work for you before? Magnetized? Not likely. Altitude? No. Workmanship more likely.

Magnetism is the most likely scenario for a sudden increase in rate like that.

A modern Zenith Defy was brought to me by a collector who wanted it “de-magnetized”, as it was out minutes per day. I corrected 5 problems with it that had not been observed by a previous technician. It never went near my de-magnetizer. It now runs within 5 seconds per day. I might have had a better result, but the watch was only on my bench for less than half an hour, and he took it with him. I only use my de-magnitizer on watches with steel balance wheels and hairsprings, and to de-magnetize tools.

There are more magnetic fields around us than ever before, and many of them are not completely obvious. I see magnetized watches all the time, so with a rapid change in timekeeping it's the most likely cause. When Omega came out with the silicon balance spring, they cited magnetism as the most common issue they find in watches sent to them for repairs, so there's no denying it's a problem. The good thing is it's easily fixed, often without opening the case, so it's something that is easy to eliminate as the cause first.

The next thing I would suspect in a case like this is the balance spring getting hung up on the regulator or stud from a shock, but that's far less common than magnetism.

If you demagnetize this and find that it settles back down, and you are unsure where the magnet is that's causing it, you may want to consider getting some magnetic viewing film:



This film can show you where the magnets are in a device like my iPhone on the bench there:



@STANDY has said many times that there aren't really any concerns with magnet when airport scanner are used, so it's likely proximity to some device that has a small but strong magnet in it.

Cheers, Al

Al's explanations are the most plausible and likely. However with the scenario you proposed it would be problems with elevation rather than altitude , unless your wife has the ability and proclivity to fly on her own 😁

Friggin' May snowstorms.

Back to the original question. There is a correction to the resonant frequency of a damped harmonic oscillator that is second order in the drag coefficient (specifically in a watch movement, I guess it would be second order in the ratio of the drag on the balance wheel to the moment of inertia of the balance wheel). And the viscous drag from air decreases by about 14% between sea level and 5000 ft of elevation and another 12% going to 10,000 ft. So it seems that there should theoretically be a small dependence of timekeeping on elevation, but I don't know if it's enough to measure. The ratio is likely very small, and there could be other sources of drag that are dominant.

I keep meaning to check this with a timegrapher using a recently serviced watch or two, to see if it can be measured, but so far I haven't remembered to do it. To be honest, it would probably require a really precise and controlled measurement, using a watch with very little variation, and controlling all other factors (temperature, position, etc.).

I also dread the eye-roll I would get from my wife if she were to catch me trying to do this experiment.