I was looking at a speedmaster that has a case maker engraving on the inside of the caseback that I have not seen before. It looks kind of like a C with an oval around it. Has anyone else seen this before or know what it denotes? There is an old thread (https://omegaforums.net/threads/case-maker-on-this-145-022-78.35104/) asking this question here but it doesn’t look like there was an answer. Much appreciated in advance.