Just for illustration, here's a billboard stamp from Century Arms (one of the worst offenders). I'd say that a stamp like this is the kiss of death to any gun. Market value is one thing, but if it's so butt ugly that nobody wants it (or want's to take a chance on it) you have effectively reduced the value to zero.
In this particular case, it also has a retrofitted safety (which, by the way, locks itself on every round and makes the gun very safe...
) which adds insult to injury. I have never seen an original Polish Tokarev for sale, but I would expect that it would be close to $1k if you ever find one. Now it's a $250-$300 shooter that has been disfigured for life.