photomoof
Fred Krughoff
How rare can they be if there are two on Ebay at the same time? 😀 True collector's items never hit the public domain, they are sold from dealers to collectors/museums directly.
Actually they do go on public auction, especially now that serious collectors are aging, but they very seldom are on eBay, but it happens. EBay has rather redefined the concept of "rare."
Dealers seldom have much to offer these days, but years ago, a few private (no store, no ads) dealers sold a lot of cameras, to each other, and to collectors.
Museums don't buy much in the way of photo equipment, they wait for gifts.