Nice rifle, wouldn't worry over the BC, Mauser is pretty consistent, they rarely vary to other steel makers and the lots are the only variable usually. No need to screw up some screws to see it, - though if you do for other reasons (metal condition or a cleaning, do try and grab a shot of them)
More interested in the stock acceptance, the lower acceptance and serial is not shown, though I am sure it is right, the acceptance under the cypher I wish were clearer. Any chance of getting a better picture? Should be C/H or C/B, but I will do some comparisons to see if what can be seen matches to another stock acceptance.
I like the interwar upgrades, this rifle certainly was hidden for a time, probably until the late 1920's and then dragged out into an upgrade in the early 1930's, probably after Hitler's tyranny began. These rifles were hidden by all sides, the right, the left, even the pro-republican side, so no telling the 1918-1927 origins, but the National Socialists are certainly a possibility, though more likely a far right nationalist organization connected to the Bavaria government or Georg Escherich (EWB fame/infamy). The National Socialists were a traveling freak show when these were hidden, though Röhm was a big player early on in the EWB movement (he was instrumental in arming the EWB and later became an arms smuggler)
Anyway, it would be good to see the RS, but I assume it will date to the other features (RB & TD), which is probably mid-1930's. Early conversions are next to impossible to find, maybe a RS sleeve at best, - which in my mind has always meant that very few early conversions survived a subsequent upgrade. Though in this case your rifle was probably never upgraded until the nazi era.
Nice looker anyway!
