Conn 2F New Wonder Bb Top Action Tenor
Date: 1927. Owned by Lewis Kahn
The Tenor Horn is, as far as I am aware, essentially a smaller bore version of the baritone. Popular in the 1800's through the 1920's. The 2F was from at least 1919 (but probably earlier) to at least 1927. It was probably discontinued no later than 1929. As measured by the owner Lewis Kahn it has a #4 bore, 0.531". For comparison, most Conn baritones and euphoniums are a #5 bore (0.562").
What Conn said in 1924:
The New Wonder Tenors presented here have been especially designed and voiced for military bands. They possess a powerful, sonorous quality of tone, which makes them superior to Slide Trombones for tenor parts in bands. In foreign countries the Tenor horn is an important band instrument, and many Conn Tenors are shipped abroad.
Attention is called to the way in which the valve slides turn upward from the orifices in the valve casings. This prevents the accumulation of water in the valves. The water key is situated at the bottom curve of the mouthpiece, which enables the performer to drain his instrument completely and easily.