I was trying to determine what year S&W started drilling and tapping their revolvers for scope mounts. All of my stainless 22's are drilled but I was wondering about the other models. I am going to put red dot sights on a few of my revolvers and I hated to uppack all of them out of the safe to check. Any help would be appreciated.

1993, according to my copy of the Standard Catalog of Smith & Wesson, 3rd Edition. But it looks like some models didn't get factory D&Ted until later (like the 610 with the -1 in 1998).