Conn 80H Medium Symphony
Date: 1924. Previously owned by Valerie Brostowski
The 80H Medium Symphony was produced between either 1921 or 1922 and at least 1927, presumably up to 1929. It was probably a #3¾ bore, which is 0.523". As can be seen in the picture it has the tuning in slide ("TIS"), which means that the screw in the hand slide is used to tune the instrument. It also has an F attachment, which would have been operated by a thumb strap.
What Conn said in 1925:
The medium bore Symphony gives a broader tone than the [other] models but does not have quite the deep, sonorous quality of the bass. It requires less effort to fill, however, and oftentimes is more desirable than one of the larger models.