Well, Jürgen, Bischoff is a good guess, the casting of the cross-head support is very typical.
My guess, however, is EPD (E. Pässler, Dresden) from the 1950s. I will attach a photo of my large EPD engine, DDR/GDR 1950s. EPD either used Bischoff parts or must have shamelessly copied them.
I have not seen any EPD engine with such a boiler/boiler house so far. Home made? Pressure gauge and fitting seem to be Märklin!?!? [ Guests cannot view attachments ] [ Guests cannot view attachments ]