With the A&D boxlock action, chopper lump barrels and Greener crossbolt, it is Gebrueder Merkel's model XXVI/77 IMHO. (There were, besides Gebrueder Merkel, other gunmakers run by other members of the Merkel family before WW2, f.i. Ernst August Merkel - EAM, Bernhard Merkel - BEMESU, Oskar Merkel _ MERCO)