I have these 2 similar trains in my collection that I have never seen in any catalogue.
The gauge is about 22mm inside rails but the size is just slightly bigger than Bing Tischbahn. The loco is 90mm, the tender 70mm and the coach 85mm.
The tracks are just a circle with rather small diameter so the train has the wheels accordingly.....
The lithografy is very similar to the Schoenner 000 trains, so this is one of my guesses. But I have read also that the smaller 000 Schoenner trains from as early as 1902 where made by Issmayer?
I am sure you will make some light in the subject!
Regards,
Manuel