Joe, The "Big Book" SC of SW wasn't a lot of help. The authors even admitted that the quantity produced was uncertain. The Model of 1989 began as the 625-2 full lug 5" barrel. The 3 & 4" barrels followed but were discontinued in 1992 with the exception of the Mountain Guns.
Sounds to me you have yourself a keeper. Hopefully someone else more knowledgeable will chime in.

__________________
Don't You Ever Wash That Thing