Hi,
as I'm not very interested in stampers, so my knowledge about them is very less, but browsing my database its probably not a BING or DOLL, FALK, PLANK or MÄRKLIN...
My first thoughts were it could be a HESS... unfortunately HESS did only made double stampers and they looked different...
It also could be a KRAUSS(& MOHR) or a PRIMUS (Zschopau) but they also look different...
The bell-shape of the stampers is very charcteristic and should be an identifying fact.
I guess its likely more ARNOLD or BECKER who produced this one.
Greetings from Solingen
Rainer