Sounds like a nice rifle, what is the serial number? What suffix range is it? It should have a suffix, probably an n or o block, which would be an earlier rifle. This rifle was actually made during the war, stayed in German hands and received at least a couple visits to an ordnance depot. Obviously the rifle was upgraded early (probably mid-1920's), looks like an early re-barrel around the same time, mid-1920's probably (Simson made barrel, probably early, but need more pictures to say more, but a lower FP means early) then in the early 1930's, after 1934/5 (the BSW components) it saw a couple more visits (another upgrade & re-stock). I assume the stock is shown BSW marked, but BSW made a lot of handguards too.
The work was done at Kassel (late work though), discussed recently in some detail. In the republican period Cassel/Kassel was one of the two premier ordnance shops in Germany, almost everything was done there or in Spandau, later some other operations opened up, all illegal, but then again the French and Belgians didn't give a damn for legality (as defined by Versailles - which itself was a ethical and moral outrage, but the French and Belgians couldn't even honor a diktat they "dictated", so who can expect the Germans to have done so...)
Do some more pictures, the stock, the barrel (does it have a code, this can date the barrel, lacking would be very early) and the serial. These things tell a story and when you leave out details we or I have to do a lot of guessing. Serial numbers are nothing to keep out of the discussion, looks like 3179, probably n-o block, - it is an old wives tale about showing serial numbers carrying risks.