MR gives you a date of Dec 1979. So it was probably built in 1980.
Check the headbadge, if original, for little numbers- a tiny stamp, 4 digits, like 0310... that would mean 31st day of 1980 for example.
They offered those in Red/yellow, Blue/Silver and GReen/Yellow.
IF it's a small frame, it's a Stingray II and would say so on the top tube. Not the most desirable Stingray but still cool and still made in Chicago.
--Rob