A watch that has passed a battery of timing tests administered by an official chronometer-certification agency such as COSC. Decades ago the word was used differently, and meant a timepiece with a so-called “chronometer” or “detent” escapement, or any very accurate timepiece.
All items in C:
- CENTER, OR SWEEP SECONDS HAND
- CHAPTER RING
- COLUMN WHEEL
- COSC (OR C.O.S.C.)