I thought it might be just after WWI for a reason the pictures might not show (well). On the right barrel's flat, nearest the breech and farthest from the fasteners, is a word in Cyrillic script. See http://s1087.photobucket.com/albums/j478/DaveinMaine/?action=view&current=100_0590.jpg the lower right of the frame. One of the letters - the fourth from the right - resembles the Greek letter theta, which my research of the Cyrillic alphabet tells me was dropped from Russian about 1918.

Any idea on what the stamps mean? We've been operating under the assumption that the 70 on the left barrel's flat means a 70mm chamber, but measuring it (admittedly not with a proper chamber gage) came up a little short. The forcing cones seem short, but it was a bit hard to feel where the chamber ended and the cone started.

fiery, dependable, occasionally transcendent