Questions about what I think is a frankenluger

[Knight Diver]

Last weekend I saw a vendor at a gun show trying to sell a "1906 Navy Luger" that was very suspicious, even to me, a newbie! I got to handle it and this is all from memory.

The toggle had DWM marking on it. That seems proper.

The frame had no date on it at all. Didn't look like it was polished off even though it was refinished. It looked like it was never marked with a year. First question is what kind of frame would not have a date on it?

The barrel had no serial number on it. Second question is does that necessarily mean a replacement barrel?

On the right side of the frame there was one proof mark. It was a "crown N." That isn't right for a navy luger. It should be "crown M," correct?

The side plate had no serial number on it. Does that mean it was replaced?

The vendor was an older gentleman with lots of older guns he was selling. I didn't want to be rude to him, but I think he knew what he had and was trying to find a sucker. His asking price was $6400. That's right. Six THOUSAND four hundred.

I think it was parts from a standard military luger with a replacement barrel made to look like a navy luger. Can some of you more luger-knowledgeable folks enlighten me?

Thanks!