With the gauge in a circle would but it before 1939. And I agree with the 10.16 or 3.15(313,318 or whatever is below 10.16) being the date, but a better pic would reveal the truth. I don't see the Belgian Perron stamp; therefore, it may be a German double with Belgian barrels. My concern would be the screw thru the head of the stock: was it original or has the head of the stock cracked at some point.

Kind Regards,

Raimey
rse