Date: 1920's 1930's. Owned by Jeff Mitchell
The 16L is a Low Pitch only bass bugle in G or F. In the 1934 catalog it was called the Long Model Baritone G-F Bugle.
What Conn said in 1934:
The addition of baritone bugles rounds out the musical performance of a corps to a surprising degree. Built in G with F slide. Length 29 inches.