Conn 4H Medium Bore Artist
Date: 1924. Owned by Jim Weltman
Instrument has a #2½ Bore (0.485") and has optional bell sizes of 6 1/2" or 7". This model 4H was produced between 1919 (but possibly earlier) and probably 1939.
What Conn said in 1931:
This medium bore Artist Model Trombone is very popular as a solo instrument, and is much used in band work. Its tone, though quite brilliant, has a delicate coloring and sweetness which have given it a large and enthusiastic following. The slide action is very fast, and the fitting of the slides to the stocking is very close, eliminating the slightest chance of leaks; well balanced. Tuning in bell; key of Bb; bore .485; 6 1/2" or 7" bell.