“Might do a write up on it if anyone's interested”
For my part? Spare me the boring story, You have just purchased a comparator.
I know he calls it a head space gage, and reloaders with the lack of "Experience" do not know the difference or understand the principal of the 3 legged chair when compared with the 4 legged chair.
For years I thought reloaders believed head space gages were made on Mars, then I realized I had more confidence in their ability than they did, reloaders, not something from Mars.