HERE WE GO AGAIN!!
Let's see now---we've mentioned "old" and "vintage"------and we have a picture of a post-war revolver----and mention of a "pre-27" (more correctly known as a 357 Magnum).
It's probably just me, but when I see "old" and "vintage" (and mention of screwdrivers), my mind just automatically goes to pre-war-----and a screwdriver for a pre-war 357 Magnum (a pre-pre-27??) is generally considered to be unavailable----or necessitating a second mortgage if you find one.
Okay, as an aid to selection of a screwdriver that will work on any post-war target revolver (also autoloaders---or "bottom feeders"-----or maybe "post-revolvers"---and maybe "pre-ray guns"), it's off to ACE Hardware with you. If you're persnickety about a period correct screwdriver (so you can knowingly refer to it as a SAT---and then glance around the room to see how many folks don't know what you're talking about----also how many are scowling----and how many are laughing), then drag out your copy of SCSW-4 (some more insider lingo there) and go to page 55. There begins a section on screwdrivers for S&W products from 1880 on up. (And you'll very likely find the same in earlier editions of SCSW----if you don't go too early.) Once you've figured out what you're looking for, prowl through some of those big boxes of junk you see at pretty much any gun show, and you'll come up with what you need. I don't know what you'll be asked to pay, but it'll probably be less than lunch.
And finally, if you're hunting a screwdriver (like a jeweler's screwdriver) for a pre-war S&W target sight, go to Lowes. Get a "Precision Screwdriver Set" (Part #0525844), and go back home. When you open it up to see what's what, you're going to find one or two screwdrivers that'll fit any of the pre-war sight screws. You'll also find handles on these tools you can actually hold onto with your hands instead of just with your fingers----and you're going to find that's a good thing. You're also going to note you paid $10-$12 for this set of 10 screwdrivers, and pretty much automatically figure they're no damn good. You'll be in good company, but know I've had my set for several years----and everything's fine (the two I used right along, a couple more I used to fix eyeglasses a time or two, and the rest of them that have never been out of the case).
Ralph Tremaine