From a 2012 Breitling forum post in reply to a question about the B-1 calibers and COSC certification/accuracy....


All Breitling 5X ("Quartz I") and 6X ("Quartz II") calibers whether COSC certified (post 2000) or not (pre-2000) easily maintain COSC quartz specifications (+/- .07 sec/day = +/- 25.5 sec/yr) in actual use. The thermocompensated caliber 7X pieces accuracy is even tighter, often exhibiting as little as +/- less than 5 sec/yr. The one exception is the caliber 70 installed in the analog UTC modules. The reason is obvious, there is no second hand on the modules, only hours and minutes. Even so, if the "mini" caliber 70 did have a second hand in place, it would most certainly also run within COSC quartz specification.

In view of the above, the year 2000 remains a benchmark time hack (tongue in cheek there...) because that was the year Breitling made the brilliant marketing decision to submit ALL their watches, the complete model lineup, to the COSC for certification. Mechanical or quartz, every single piece after 2000 comes with certification certificates. To this day Breitling remains the only major watch manufacturer to do this.

More information is available here... The Breitling B-1 Don happens to be one of our long time members and provides more B-1 information on his site than you will ever need. Hope this helps...
Best,
Ron