Repeat Reading Gage - DIYSwede's "Cheap-O-Meter"

[Toolmaker51]

Yeah, I'm pretty much a sucker for anything0'meter too, long as it applies to accomplishing work.

Occurs to me frying pan version can be 'zeroed' or nearly so by rotating either more or less than 120° around the indicator.
Then, what ever diameter, divide available plate area by that; into 'zones', that could overlap.
Comparison with the Repeat-O-Meter should agree if perfect flat; because pan is a footprint, and the ROM is rather linear. Perfect flat
not much an issue unless checking a large array of small items. That's a good job for the smaller surface plates; less area = less potential deviation.
Very few times did I require supreme accuracy. It was not controlled environment, a high grade plate, or all that clean. So with three ~4mm bearing balls, three drops of Super Glue and a 50 millionths indicator...We made a slew of valve plates for high pressure air valves. When high pressures erode ports, leaks ensue.