It may be that M. Orgis applied little effort the sporting weapon and that the mechanics marks of K, OG & EA are all from Suhl. K & EA are common for Suhl proofed examples and right off I guess OG could be for Otto Günzler of Suhl but I'm sure there are other possibilities. Not too many choices in the short mm range in 11.7mm, maybe 11.7 X 49R? It was available during that period and the base(14.4mm) & rim(15.9mm) seem similar.

Kind Regards,

Raimey
rse