Steve, Can't tell you about the worth but this is from the rec.guns FAQ on Smith Revolvers (
http://www.recguns.com/IIIB2e1.html)
Model and Dash numbering system
--------------------------------
Model 10
-1 1959 Sesignation for Heavy Barrel
-2 1961 Changed extractor rod thread to LH on standard barrel
-3 1961 same as above, for heavy barrel
-4 1962 Screw in front of trigger eliminated
-5 1962 1/10" to 1/8" front sight, on standard barrel
-5 1962 Screw in front of trigger guard eliminated on
heavy barrel model
-7 1977 Change to put gas ring from yoke to cylinder
-8 1977 Change to put gas ring from yoke to cylinder
on heavy barrel model
Hope this helps.