]
That's my understanding as well. I'm not sure it has much impact on price today, but it's a nice option that sets some apart from the pack. I believe all T40 FL (fretless) models had the rosewood board.
Nice! Sounds like you've got a very nice one.
The latest version of the T40 Info sheet is here:
T-40 infosheet
It includes rough dating info though this is pretty easy to date. Yours has blade pickups which were introduced someone in 1981 but also the metal nut and pick guard half-drilled indicator dots (both likely dropped in '82), so it likely dates to 1981-82.
Play it in good health!