2 x 1916 DWM markings questions

[Zamo]

It's not mine...yet. It comes with a "+" marked matching magazine, and is all matching, but looks so nice (albeit patina'd, so I think it's orginal), that I am questioning it according to these two marks that raised my eyebrow. The dealer wants $1350. What do you think of that price?
Here are some more pictures:






It looks nice to me, but some of the pictures aren't quite crisp enough to remove doubt.
The grips are s/n matching as well. I am a little concerned by the lack of wear on areas like the side of the front sight barrel flair (what ever that is really called), and the sideplate, which always seem to show SOME wear...I really don't want to buy a previously refinished piece, but it's a remote transaction, and the seller doesn't do a three day inspection...which also has me worried.