Pan American 56A Short Model
Date: 1946, owner unknown
The "Pan American" line of band instruments are Conn's "B" line, and were made by Conn in Elkhart, Indiana. Frequently they were produced for a specific vendor such as Sears. This instrument has bottom spring valves. The bore size is a #2½, which is 0.484".
The 56A was the predecessor of the model 58A, which is essentially identical except for a main tuning slide rod which the 56A has and the 48A doesn't have.
As far as I can tell at this point, all Conn cornets built before 1958 take a short shank cornet mouthpiece as opposed to the 2¾" "Bach-style" long shank cornet mouthpiece. The long shank cornet mouthpieces won't properly fit a pre-1958 Conn cornet and won't give the proper intonation or playing characteristics of a short shank cornet mouthpiece. All of Conn's "Connstellation" cornet mouthpieces are long shank mouthpieces. The "Improved Precision" Conn mouthpieces such as the Conn 4 are long shank if there is a "ridge" halfway down the shank, and short shank if there is no ridge (in which case it is a "Precision" mouthpiece). All Conn cornet mouthpieces built before the "Improved Precision" series (ridge), such as the "Precision" series (no ridge) are short shank mouthpieces.