I have got hold of a soprano mouthpiece which looks old-ish, possibly vintage, likely ebonite, but all that is stamped on it is "R4" - there is also an indented line around the piece about half way up which used to be white/cream coloured. There may have been other logos but it is quite worn so they may have rubbed off. Any ideas for who made it? Yanagisawa metal pieces are R4, R5 etc but this is ebonite.