help to identify 1918 1920 9mm DWM double stamp

[padredan]

i hope i have this in the right thread, if not let me know , trying to identify another luger i acquied, it is a double dated 1918 1920 chamber stamp,DWM,9mm, pistol is in very good condition and shoots well, very nice bore and everything matchs, serial number 3881 not sure of the alpha letter, maybe you can make it out in the picture, left side infront of the serial number circle S,right side six proof marks, barrel has serial number with 42 over 882, i am sure it has been replaced, any help identfying it would be helpfull