The ones made after Conn moved the plant from Elkhart to Nogales Mexico in 1968 had some serious construction quality issues. Poorly fit keys, posts in the wrong position, poorly fit springs are a few of the things I remember from working on them. The common wisdom is that if the serial number had the prefix N it was made in Nogales Mexico. This is only partly true. The Shooting Star models with serial numbers starting with M, N, P, R, as well as serial numbers from 83,000 to 128,000 were all made in Mexico before the plant was moved back to Elkhart in 1980.
My experience is that once repaired, they actually play quite well similar to the vintage horns, but repairing and maintaining them is a real headache making them not worth the bother.