Was with a friend who bought a war time marked camera in Brno. It had been defaced, and the thought was that during the post war time, having German war time anything was considered to bring the wrong sort of attention from some in authority in Czech.
However, the scratching seemed stupid, it did not obscure the origin and merely lowered the value, assume it was a "shooter".
Still, it changed hands a few times and at least three people made money on it, perhaps more.
US Customs used to deface certain names, like Pentax, if they saw them coming home with citizens as the names were "owned" in the US by some of the distributors, or so I am told. I have seen Asahi Pentaxes with the screwdriver marks on the name.
Nazi stuff remains creepy to many, myself included, though I found an interesting Mauser, Brno I believe, which had German, US and Israeli proofs and was rechambered to .308 Nato-- history was interesting, and the good guy marks out numbered the bad guy marks.
I do know a dealer who was taken in on one of the fakes on eBay-- it happens, and I have a "Yuri" ;-)
Regards, John