Chad,
I've did some digging and i can't find my old reference book that would give me some dates to put to serial numbers. Sorry about that!
Valmet came into the US under their own name in the early 80's, and the first gun i got in, has a serial number of 205.... I have a VERY early set of experimential bbls and they are #201.... One of the last serial numbers i got in before Valmet USA closed it's doors, i believe is close to 282..... I guess you can put your's in there some place.
EVERY Valmet action had a set of bbls with the same serial number when it left the factory... BUT i know Valmet USA use to rob bbls to fill orders too.
Doug,
I never compiled a list of numbers and years
DM