The 11M's are fairly rare. Conn intruduced the 11M in 1968. The first 11M's were pretty good. They're basically the same horn as the 12M, only with a low A extension. What happened was that shortly after the 11M was introduced, Conn was sold to MacMillan. MacMillan moved all production to Nogales, AZ and later Mexico and quality really went down. If you are lucky enough to find an 11M with an "L" prefix in the serial number (indicating 1968) it's a pretty good horn. Those made between 1969-1970 were not as good, and those after 1970 (Serial prefix "N") are trash. I have a 1958 12M that is not playable. It belonged to a school, and I bought it in need of a lot of repair. It has some pretty bad dents and needs a complete overhaul. I'm not sure if I want to try to restore it or just use it as a parts horn, actually. I just finished restoring a 1930 New Wonder series II transitional baritone; often called a Mulligan after Gerry Mulligan. It's not for sale though.