Lancaster, except for the DWM receiver inscription and the circled B stamp (these B stamps were used by several countries, France and the Soviet Union among them), this rifle Looks like a typical Mauser C, as imported by Tauscher to the USA. the inscriptions "spitzer bullet" and "Germany" look like "Mauser" too, and the thing even has a pre-WW1 Mauser factory buttplate with the Waffenfabrik Mauser WFM logo. As I wrote elsewere, DWM sometimes had their "promotional gift" rifles put together by their subsidiary Mauser, because DWM lacked a commercial shop of their own.
BTW, about the DWM-Mauser Relations: Many of the Brazilian 7x57 1908 military rifles are marked on the receiver wall "Deutsche Waffen- und Munitionsfabriken Oberndorf a.N."! DWM, Berlin had the order, but for capacity reasons subcontracted the actual making to their subsidiary Mauser, Oberndorf.