Ahh, I think this is why I couldn't get deep into vintage Omega ( apart from the cost). Even with all of the wisdom here, there are differing opinions and not a satisfactory definitive answer. An auctioneer for a very well known auction house was recently bemoaning this with regards to Rolex and aftermarket Singer dials. How some people would believe they had an original dial then others would chip in saying it wasn't original to the watch but fitted retrospectively. These watches cost tens of thousands and several cases have gone to court!