Date: 1924. (Drawing)
The 3A Wonder is the High Pitch version of the 2A Wonder. It came with extra slides for both high and low pitch. The 2A Wonder looks remarkably similar to the 1960's 2A Victor. I suspect that the 1960's 2A is an updated version of the 1920's 2A Wonder. The 3A Wonder was produced between at least 1919 and 1927 and has a #½ (0.425") bore. As far as I can tell, the name "Wonder" was dropped at some point in the late 1920's.
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.
What Conn said in the 1920's:
"...has the true cornet tone, offering a slightly higher voice to the band in which it is used. Provided with the new adjustable tension valves found exclusively on C.G.Conn products."
Weight: 2 lbs., length 14", bell diameter 4½". The 2A is the low pitch version, the 3A the high pitch version.