Thank you very much for viewing. This is an A. Courtois mouthpiece (made in France), model E-1. Currently, Courtois mouthpieces do not have this size, and there is no record of it existing in the past. I contacted several shops specializing in mouthpieces, and they said: * They have never heard of that size. * It may be a size specially made by a craftsman overseas before Courtois was acquired by Buffet Crampon (2006). * (When I told them the cup was quite deep) It may be a mouthpiece made for euphonium, bass trombone, or bass saxhorn. * However, someone may have engraved the markings themselves. I acquired this about 10 years ago, but I haven't used it much, so I don't even remember how I got it. The condition is clean. Please consider this item, understanding that it is a used product.