Gosh it probably is a W, again I just can't make it out very well. Do me a favor Dean and go the link that Garth posted earlier and I copied below. Scroll down a bit and on right side there is a black and white drawing with German description of what I guess is gunmaking. I have a friend that speaks German fluently and would ask him but he is overseas 7 hours ahead. Anyway if you go bottom of the drawing there is a capital "M" that appears to be at the start of the Word Mann, I guess. That letter has same looking characteristics as the one engraved on the gun.
http://www.germanhuntingguns.com/abo...s-dealers-f-j/
I also just went to Google at this webpage. Below the M and W look very familiar but there is a break on the M under that first upstroke that is not on the W. I don't know.
http://www.fontriver.com/i/fonts/ger...d_specimen.jpg