I understand the quality issue, that's not my question. If a repairer in the 1950's used a cheaper generic crystal how would the owner of the watch know? There were no collectors back then. He wouldn't have a clue about the Omega mark on the crystal, and wouldn't be looking for it unless there was an advertising campaign to inform the public. They just wore their watches and had them repaired when they stopped running, they didn't take a magnifying glass out to check for something they didn't even know existed. And dials were routinely refinished, too. Perhaps repairers were told to inform the owner of the watch that a genuine Omega crystal was used in the repair. So that was my question as to why Omega started the marking, it's either for the end user or for the repair industry. Omega didn't start doing it for no reason. I can see why they do it today with people running around checking crystals for the mark, but 70 years ago?