I’d say 80%+ of vintage Breitling watches on eBay are fakes with a similar percentage of Ulysse Nardin.
The reason for this is that those brands in particular are far better known today than they were 60 years ago. Back then, both companies were more assemblers of watches than true in-house manufacturers. By assemblers, I mean that they purchased base movements and tweaked them to their own specifications. This made service and spare parts a lot easier and this is still done today.
Unfortunately, it also makes “upgrading” a generic watch (which likely had a very similar movement) by repainting a dial and replacing a few parts very easy to do.
My advice would be not to buy Breitling vintage watches on eBay unless you know what you are looking for in precise detail.
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