I tend to agree with the above.
There are a few German sites about Eisenwerke Gaggenau and it is interesting to notice the change in the name of the factory:
1873 Michael Flürscheim und Franz Korwan kaufen am 1. Februar das Eisenwerk von Ludwig Klehe
Firmenname: „Korwan und Flürscheim Eisenwerke Gaggenau bei
Rastatt“ (vormals Louis Görger)
Do you remeber where the Diana (Mayer und Grammelspacher) factory was located? in Rastatt!
It seems very likely MGR bought the forged/cast parts from EG in rough form to create their own GEM?
A few years later the EG factory got a new name:
1880 Theodor Bergmann, ein Herdfabrikant aus Konstanz, tritt in die Firma ein.
Emailierwerk, Stanzerei, Vernickelungsanstalt, Buchdruckerei, Schreinerei und Kunstgießerei werden eingerichtet. Neues Produkt: Badenia-Fahrräder
150 Mitarbeiter
1884 Bergmann wird Teilhaber. Firmenname: „
Eisenwerke Gaggenau, Flürscheim und Bergmann“
So there is the connection with the Bergmann marked GEM's.
The Jean Marck GEM's are different in construction and (in my opinion) made by a Belgium? factory.
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Frank