A few points of clarification here... my knowledge on these is incomplete but I've done a fair amount of study in preparation for my own build.
To start off, a great resource on these is a series of blog posts that Don Hillenbrand wrote about trying to authenticate what ended up being a fake laser.
This TPZ thread is an awesome resource and provided a lot of information for the above blog posts, though some photos are broken. It's where the diamond crosshatch was discovered to have been present on the first version of the props as seen in "The Cage."
Some photos of the Jein fixed-barrel hero (the same prop that Karl/phasepistol documented):
As to your history, if you'll permit there are a couple of things I want to comment on
You have the modifications backwards - the silver paint, typewriter keys, and gears were added for "WNMHGB" and present in later reuse. The first use in "The Cage" was the plain appearance.
I'm not sure what you mean about the bodies being "slimmed down" unless you are referring to how the pistol Spock uses in WNMHGB does not have the embedded horseshoe magnet. I believe other than that and the presence or absence of a sight recess, the bodies are uniform between all variations.