Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Your guess that it might be a GDR/DDR produce is an understandable one, but I am sure this is not the case here.

I'd rather say this a very rare model made by WGL/HGL (even the name is up to discussion: Wilhelm Groening, Lüdenscheid, Germany or Heinrich/Henrich und Groening, Lüdenscheid), the mysterious forerunner of Wilesco.
Yes, I know, most of their engines look more like clumsy Wilesco-fakes, but there are also some engines attributed to this maker which look much more decent and well made - e.g. a really nice overtype (one once owned by Mirko...) and the cylinders are the same.

A very nice engine, I do understand why you wanted to have it.

PS: Lüdenscheid is a small town in Western Germany...