Date: 1958. Owner unknown.
The main differences between the early and late models 14A are the straight bracing of the late model, the addition of a 3rd slide ring and the switch from a short shank cornet mouthpiece on the early model to a long shank cornet mouthpiece on the late model. The "late model" 14A is very similar to the 15A. It has been pointed out to me how to tell the difference: the position of the bell brace with respect to the leadpipe finger hook. On the 14A/18A that bell brace is right next to the finger hook. On the 15A/17A the brace is an inch or so towards the bell. Apparently the tuning slide connected to the leadpipe has an expanding bore; the bottom tube is a larger bore than the top tube. The "late model" 14A was built from 1958-1960. The bore size is a #2½ (0.485").
What Conn said in 1958:
Professional bore designed for the student. This short model cornet has the full cornet tone found only on other higher priced instruments. These features are needed by young players: full bore, crysteel foolproof valves with noiseless nylon guide, adjustable third valve slide ring, Lustre-Conn finish.