Howdy
As was mentioned, as time goes by firearms evolve. Cost is often a factor. All Handejectors were 'Five Screws' when they first appeared at the end of the 19th Century/beginning of the 20th Century. Threaded holes cost money to produce. More than machining special features. Around 1955 S&W eliminated the upper side plate screw by machining a lip into the side plate that fit into a slot in the frame. Around 1962 the screw in front of the trigger guard was eliminated. Ever since, all S&W revolvers have been 'Three Screws'. Yes, they are still Three Screws.
Frankly, one reason (out of many) I like Five Screws so much is it is much easier to remove the cylinder stop on them than with a Three Screw. The screw in front of the trigger guard housed the spring and plunger that operated the cylinder stop. Take out the screw, then the plunger and spring. Much fussier with a Three Screw, trying to futz the spring out from its hollow in the frame.
In this photo, the Five Screw K22 was made in 1932, a little bit before my time. I bought the Three Screw Model 17-3 brand spanky new in 1975. Bought the Stainless bazillion shooter a few years ago, just on a lark. Not really crazy about modern Smiths. Yes, it is a Three Screw.
The hole under the cylinder latch is where the hammer stud is pressed into the frame. For a long time, the stud was left sub flush in the hole. Later guns had the stud a little bit longer and it was polished flush with the side of the frame. You have to look carefully, but it is there. Just like the trigger stud on this old M&P. Look carefully, it is there, cut off flush with the side of the frame and polished to be almost invisible.
I just looked at that 'bazillion shooter' 22 and frankly, I can't tell if these studs are present and polished flat, or if the studs are pressed into blind holes. Have not had that one apart yet to see.
Do I prefer Five Screws to Three Screws? Absolutely! But I always prefer an old gun over a new one.
