Yes. As stated, I'm in the middle of a rebuild. That's where I got a sampling of keystems to measure. Since they were originally made with a punch-die, they're not overly precise and you need to look at several copies to guess what the original, intended measurements were meant to be. I'll admit my diagram has a lot of guesses, usually based off the simplest and most straight forward possibility.
In terms of why, many older keyboards have extensive corrosion damage. In my experience rebuilding Beamsprings and Model F units, the top-plate and back-plate can take on a lot of rust, but still clean up fairly well. The spring-steel of the beam and fly springs is also fairly resistant. Springs and O-rings are easily replaced, and the rest of the key-switch parts are plastic. While the original stems appear to be made from stainless steel, they can get really chewed up inserting and removing the, especially if there has been any moisture damage. They're also, in the grand scheme of things, one of the easiest parts to re-make (that isn't already an off-the-self part, like the o-rings or springs)-- as long as you have the dimensions.
There are alternative motivations as well. As mentioned, I'm interested in making stems from alternative materials, both for the look and possible difference in feel/sound. The longer term motivation is to design a stem that can accept MX keycaps, but before we get there, I want to make sure I understand how the basic stems were made and fit. (And yes, I'm aware a few others have looked at MX stems before, but as far as I could tell, nobody has ever bought the project to conclusion; it's a long-shot for me as well)
