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Tools · 9 January 2010, 02:23 PM

COSC did not exist until after 1973. What COSC did was standardize the Swiss standard at -4 to +6 seconds per day (roughly... it really is more complicated than that)..

So, any watch after 1973 that has Chronometer on the dial had to have met those standards and been tested..

From ~1960 until COSC Standards in 1973, the "chronometer" standard was -1/+10

9 January 2010, 02:23 PM	#3
Tools TRF Moderator & 2025 Titanium Yacht-Master Patron Join Date: May 2007 Real Name: Larry Location: Mojave Desert Watch: GMT's Posts: 43,865	COSC did not exist until after 1973. What COSC did was standardize the Swiss standard at -4 to +6 seconds per day (roughly... it really is more complicated than that).. So, any watch after 1973 that has Chronometer on the dial had to have met those standards and been tested.. From ~1960 until COSC Standards in 1973, the "chronometer" standard was -1/+10 __________________ (Chill ... It's just a watch Forum.....) NAWCC Member