Rolex

Fwiw here is the link to my post several years ago about my Oysterquartz. You might already know this:  I have since learned that the first thousand or so pieces that they made had a different quartz oscillator. Also, though these early date only versions were not submitted to COSC, the same movement with the day/date version were submitted to COSC. After they changed to the new quartz oscillator version, all versions were submitted to COSC.

As another point of interest, about nine months or so after I had my Oysterquartz it suddenly became not very accurate, so I wrote the president of Rolex USA to complain and I received back a personal letter from him inviting me to send him the watch to be repaired. Now I wonder if they in fact replaced the movement with the new version quartz oscillator.

www.watchprosite.com