Certainly a nice rifle.

Wilhelm Brenneke's lifetime achievements are described in a 7-page article in the 1960 Gun Digest. These include the design of the 7x64 Brenneke cartridge.

Also, I presume that large side button visible is the hinged floor plate release he also invented. The item marked "Kammergriff verriegelung" is another invention, to hold the bolt in position to prevent it being inadvertently raised, (Kammergriff means bolt handle and verriegelung means bolt lock).

Yet another invention pressed against the lengthened cartridge extractor as it moved rearward. This did away with the looseness of the bolt, eliminating clatter and rattling as it is moved back and forth.

I don't know the value of the rifle, but it stands out from other unmodified Mausers of this period. I would think it quite desirable by collectors of this era.