A few weeks ago I saw an Astra 300 (.380) at a local small shop. The price was good - under $400. I went home, thought about it, then called a few days later to see if it was still there. It was, but at a price of $1200. Why the increase? It's Nazi marked, they said. I went back and looked at the gun recently, and sure enough, barely visible with a magnifier, was a small, faint, Waffenamt (eagle) mark that they had missed. Even the salesperson had to search for it. But, it is Nazi marked, I guess, and they can, and should, charge what they think the gun is worth. At $1200 - not for me.
Would that be enough of a mark to satisfy a collector?
I did some research and it seems that collectors also go by the serial number range, so maybe that answers my question.