I just purchased this 25-5, made in 1980. I did not realize it had the wrong grips on it till I got home and removed them. They are dated 1988. The gun and grips are in excellent shape. I am OK with them.
FWIW, I was almost suspended from my PD in 1977 because I carried non department issue HKS speed loaders in my jacket pocket. I had them at least a year or two prior to that. I also got in trouble for putting a set of Pachmayr rubber presentation grips on my Model 66 that same year.
It appears that the switchover was in late 70's to early 80's with L frames first, then K and N frame . . .
To further add to the discussion there were target stocks made earlier than the 80's that were very similar to the speed-loader cut-outs but for a different purpose.
A couple of commemorative S&W's guns that come to mind were the 125th Anniversary Mod.25-3 in 1977 and the Texas Ranger which was introduced much earlier. Their cuts in the stocks were to display the commemorative symbols rather than to accommodate speed-loaders.... but those special features convinced some people the cut-outs were available on much earlier guns....