OK, discounting
Rolls-Royce Corp (which is what Allison is now known as), the last significant Derby turboprop event was an amendment to the Dart Type Certificate in 1985, with the addition of the Dart 552 (for the F-27/748).
Unlike the Dart's, the Tyne TC is no longer current as only military applications are still flying, so it's still a toss-up between those two engines as to which was last in production.