My suspicion would go this way too. Not proofed, but converted.

This looks unofficial, but the z instead of c (German “spezial”) is a strong clue. I haven’t had my coffee yet, but unless I’m missing something obvious, the words above make no sense to me and might be a name?

PS: The second word may be a town in Germany, Lenggries.

PPS: So I read what has to be the converter‘s name as “Rossing”. No gunsmiths by that or a similar name to be found around Lenggries, but this looks like a quite old stamping, so likely long passed, without leaving a web footprint.