Perhaps the most interesting thing about target models (any/all of them in the early days) is the sights. Target sights first became available on the New Model #3----late 1870's. They continued to evolve for the next 60 years---when the "Micrometer" adjustable sight appeared on the K-22 2nd Model in 1940. That sight remains in use today----looks different---essentially the same sight.
The evolution was driven by the necessity to design a sight that wouldn't "shoot loose"---sounds simple enough to me; but I wasn't there. There never was a problem with the .22's, but as you move up what I'll call the recoil or shock ladder, there it was--the damn sights moved!!
The very first sight which was truly adjustable for windage came about in 1909-10. The sight which preceded it was simply movable----nothing adjustable about it. It was adjustable by virtue of a pair of opposing screws----which essentially locked (one against the other) when you were through adjusting----and there never was a problem with windage adjustments "shooting loose".
The elevation adjustment was a different matter altogether. With one exception along the way, elevation adjustment was accomplished with a "jack screw". It worked great for adjusting, but when you were through adjusting, it just sat there---waiting for something to come along and jar it loose. They tried all sorts of stuff to make it stay put--and failed.
Then came what we have come to call the "two screw" sight-----early 30's----only FIFTY YEARS after they started. Oh, the shame of it all!! This one has TWO screws in the elevation system---ostensibly one screw to adjust with, another to lock with. And if you use it as I've just described it (intuitively), it won't work---it too will "shoot loose". So FOLLOW THE INSTRUCTIONS!! Following the instructions is a large pain, so they kept at it-----and VOILA----the "Micrometer" sight came to be. It stays put by way of detents----spring loaded.
All that said, the "two screw" sight is the very best one ever made----simply because it is INFINITELY adjustable, and the "Micrometer" sight isn't. But the "Micrometer" sight is easy to use---AND it won't shoot loose. The "two screw" is NOT easy to use (properly), but when it is, it too stays right where you put it----no matter what.
Ralph Tremaine