The model 60 is one of the guns in which the engineering changes didn't necessarily replace an earlier version. The 60 was made from 1965 to 1988, with pinned then unpinned barrels. The -1 and -2 were special runs, and the -3 finally replaced the 60. You'll have a hard time finding a bad one. Hope this is helpful.

__________________
Alan
SWCA LM 2023, SWHF 220