Forgot to note that the D near the forend hanger more than represents sourcing of components & it may represent effort also. A guess would be Heinrich Diem of Benshausen bei Suhl. Denecke & Co. as well as Gebrüder Decker but both were in Zella-Mehlis and I doubt cross-sourcing to Z-M, but it is possible. D is a common stamp in that position & on the forward part of the right flat on Suhl sourced sporting weapons. I do not believe I've ever seen the stamp of a D on a Sauer manufactured sporting weapon.

Kind Regards,

Raimey
rse