There are few choices for Suhl mechanics that had the initials RM:
Ernst Richard Meffert
Rudolf Mhring
Robert Mller
I'd hedge my bets on Ernst Richard Meffert. As an aside for those hardcore initials folk, barrel smith Casper Schlegelmilch hung out his shingle in 1818 & continued thru several generations and there was a descendent named Caspar Schlegelmilch in the early 1900s and he passed the torch to Hermann Schlegelmilch and then, and then the concern was acquired by Alfred Menz of August Menz. So the tubeset initials CS to CS to HS to AM all originated @ the same concern & there is much more research warranted here to determine the family relationship. I'd hazard a guess Menz married a daughter of Hermann Schlegelmilch or similar.
Cheers,
Raimey
rse
