Archer
··Omega Qualified WatchmakerThe watch is not “as it came” from the factory, but it has a factory replacement case of exactly the same vintage....is that heresy?
Very few watches are “as it came” from the factory. Hands are routinely replaced, as are crowns, pushers, etc.
If you bought the watch new, and stuck it in a drawer, never taking it for service, that is an example of an “original” watch.
As for your specific scenario, it’s not heresy in my view, but something that should be disclosed if you sell it.