I think any model made while Conn made the horn in Elkhart is probably good. I believe Conn started making the Connstellation around 1956 or 58 but do not recall when production shifted out of Elkhart. I have a 38B made in 1963 and I would not trade it. I would say the best models were probably made from 1960 to 1968. I am sure others on the forum can provide more insight. If you can find one made during the 1960-68 period you will be very happy. Some players think the Connstellation has a darker edge, I do not agree. I have never played on a horn that sounded brighter, especially in the higher register. That is why I think MF was at his best during the Roulette years when he played this horn. He just had an edge to his playing on the Conn during that era.