Funnily enough I had also been thinking about the odd spacing between the "2" and the "BO". You finding the Renazzi Mario makes me think it could actually be quite plausible. No mocking from me!
Hi Trev I know the Swiss used RM at some point as a "Responsibility Mark"......Could it possibly have anything to do with that? Or maybe a German "ReichsMarke"?
I have a pair of 18 Karat gold earrings in an almost sunburst shape. Created by 2 circlets of 8 rods each. The weight is 7.5 grams each (15 Grams total) and bears the 750 stamp in a lozenge shape. One mark at the top says "2 BO". Another marks at the bottom is a downwards pointed triangle ...
http://i49.tinypic.com/nyeg50.jpg http://i50.tinypic.com/13zzls3.jpg Have a set of 4 spoons. possibly silver gilt but do not know therefore posting under silver-plate. A bit hard to see from photos, but they are very gold coloured, and definitely not silver coloured. Hallmarks are a Star, Half Moon...