DWM Navy?? Luger Markings

Hello

Some years ago I bought at auction as a postal bidder what I took to be a Navy Luger. It was made by DWM and dated 1917. However, the numbers on this pistol are not matching and I suspect that it might be the result of two pistols being put together, ie, the barrel and slide of one and the frame of another. It has the longer barrel of the Navy type when compared to the standard barrel of the Army P'08 pistol.

What I am particularly interested in are the markings on the left-hand side of the receiver which appear to be a Crown over the capital letter M. There are three of these as well as a smaller one on the pistol's toggle. I have attached an image of these markings.

Any advice as to what these stampings represent would be appreciated.

Thanks in advance.

Jage.303