Interesting. I know that during WWII wristwatches were tested to keep time correct to 10 seconds in 24 hours. (Important if you're expecting e.g. an artillery barrage to start just ahead of your infantry at a given time) If slow or fast by more than 10 seconds they'd be sent to REME for adjustment. Those that couldn't be adjusted to within tolerance were sold off to the public. Canny traders bought them as job lots, knowing that all they needed was a new hairspring, There was a big market in them after WWII. Whether they were Omegas or lesser regarded brands, they were all made to the same specification, and were a bargain.