Curious if anyone can identify what the "BC" on the right and diamond shaped mark on the left could be. For context, this is a yellow gold Cartier deployant watch clasp dated to around ~1978 based on the patent registration number engraved on the opposite end of the clasp. There are also certain clues on the watch case and movement that point to this being retailed at Cartier NYC.
The first image is a shot I took of the clasp while the second image is a much clearer example I found online for the diamond shaped mark, which appears to be a small "m" inside of a larger "C". I've seen this mark enclosed in both diamond and oval shapes on various older models.
Thank you!