Interesting hammer double w/ pattern welded tubes and from the worn marks I would hazard a guess that Emil Barthelmes of Meiningerstraße 11, Zella – Mehlis was the mechanic that Wilhelm Förster sourced for this offering. Do note that it appears that Förster either had a Quality Control Mark of "F" which he applied to the tubes & to the water-table. Also, the application of the "F" was an attempt to mask the Quality Control Mark of Emil Barthelmes.

I can't hardly decipher the G?M stamp on the underside of the left pattern welded tube near the lower rib?