A question for the tech experts on timing standards

[luger]

Can any tech expert confirm one way or the other whether Rolex has an in-house timing standard more strict than COSC. I have seen a claim of an in-house standard of -1/+5 sec/day bantered around on the forums but is it supported by any document or writing? It would seem to me that this might or could exist, maybe even in a footnote, in the tech sheets. Parenthetically, my question is sparked by the language on the Rolex guarantee about in-house testing after COSC certification and the meaning of the Red Seal hang tag. Your kind courtesy and consideration are greatly appreciated.

[watchmaker]

Rolex would like their customers to believe they can get their watches to about +/- 2 seconds. However, in practise, the sheer volume coming off the production line and going to COSC, there is too many to give that much attention.
As you get closer to perfect time keeping, it becomes harder and harder to keep regulating. To bring it down from +40 seconds per day is easy. To reduce it from +7 to +0 is very hard. It would require much longer than the 15days spent at COSC to gain an accurate picture of how well that watch will perform. So in the interests of actually selling the watch, and not testing it for weeks on end, Rolex 'settle' for COSC certification. -4/+6 is pretty good going anyway.

[Wooddog44]

Rolex would like their customers to believe they can get their watches to about +/- 2 seconds. However, in practise, the sheer volume coming off the production line and going to COSC, there is too many to give that much attention.
As you get closer to perfect time keeping, it becomes harder and harder to keep regulating. To bring it down from +40 seconds per day is easy. To reduce it from +7 to +0 is very hard. It would require much longer than the 15days spent at COSC to gain an accurate picture of how well that watch will perform. So in the interests of actually selling the watch, and not testing it for weeks on end, Rolex 'settle' for COSC certification. -4/+6 is pretty good going anyway.

I've also wondered that same thing.