The JT8D is an axial-flow, dual spool, fully ducted turbofan engine. It's design dates back to 1960 Some of the certification milestones are as follows.

Feb 1963 JT8D-1 certified @ 14,000 lbs thrust (entered service 1964)
Apr 1963 JT8D-5 certified @ 12,000 lbs thrust
Mar 1966 JT8D-7 certified @ 14,000 lbs thrust
May 1967 JT8D-9 certified @ 14,500 lbs thrust
Sep 1968 JT8D-11 certified @ 15,000 lbs thrust
APR 1971 JT8D-15 certified @ 15,500 lbs thrust
Feb 1974 JT8D-17 certified @ 16,000 lbs thrust
APR 1976 JT8D-17R certified @ 16,400 / 17,400 lbs thrust

1988 saw the end of production of the JT8D -7 thru -17's with 11,878 units being produced. Those produced by dash models are:

Pretty much by the end of 1988 almost all the -1 and -5 were converted to other dash models or were no longer in service.

The JT8D-209, which was the first of the -200 series, was certified in 1979 and entered service in 1980. Since 1989 only the -200 series JT8D's are being manufactured.