That would be a transitional model Baritone, or an early "12M", these were often referred to as a "Mulligan". The serial number indicates that it was made in 1933 (www.drrick.com/conn.html The patent number is for the rolled tone holes. The "M" in the serial number is for saxophone and was used int the mid 1920's-Mid 1930's. The letter M also signified 1969 as the year of manufacture on later Conns, but these horns did not have the patent date. These are highly sought after baritone saxophones, and they are quite valuable. If the horn is complete, without dings or any damage, it should be worth $1200-$1500 even needing an overhaul. In good condition and playable, this sax could be worth $2500-$3000 or more easily, depending on the condition of the lacquer, etc.