OK,it looks like a G&H mount, but a pre-WW1 German rifle and a pre-WW1 German scope joined by an American mount by a company founded in 1923, using germanic soldered half-rings on the scope, and then the whole affair back in Germany? IMHO it may also be a Greifelt, Suhl mount. Perhaps G&H did not invent their mount from scratch, but copied an existing foreign design. At least, the Greifelt mount shown in the Lampel/Mahrholdt "Waffenlexikon" looks just like the old Griffin&Howe single-lever side mount.