I would have to date it between 1912 and 1922 incl.( I would normally say " after 1911 and before 1923"). The nominal cartridge marking is interesting. The M88/ 8 is normally the J bore cartridge, but maybe this is modified by the SG which is stamped next to it. It seems reasonable( since "slugging showed .323" grooves") to read that as "Spitzer Geschoss", which was the S bore. The M88 would indicate an early date, but so many workers marks indicates a military surplus action, which would be post 1918. " you pays your money and takes your choice".
Mike
