It has been pointed out to me that it isn't always easy to figure out which Conn models were made when and how they compare quality wise. Quality in this case is defined as "student", "professional", etc. Although I reject that characterization to a degree, you know what I mean. Here are some tables that will hopefully shed a little more light on the subject.
Conn Cornets 1955 - 1969
Conn Trumpets 1955 - 1969