I've got a student who brought in a Conn with what I believe the serial number to be "M 212XXX" Looking at the serial number charts I was a little confused. It looked like 1928, but a different chart said something very different. It's an alto, golden brass. Rolled tone holes. The low Bb/B pads are on opposite sides of the horn. It's got an extra key in the right hand for I believe G# as well as an extra small pad behind the lower stack. Thanks for your help.