Very happy to help -- just plain fun to solve problems -- I think we all feel that way on this forum!
It's one of the things I like best about this forum!
One thing I was curious about was that it was 0 to 80 instead of 0 to 100, unless I got that wrong. I couldn't see for sure, but it looked like 40 was at 6 o'clock, so 0-80 is what I drew up. (if I was wrong, just let me know and I'll re-do it).
So... I had a look at my Mitutoyo earlier, mainly because it's handy here at my desk, and it's graduated the same way- 0-40-0. However, it's a metric dial... so I wonder if this one might be metric too?
Hang on a tic... I'll go grab the Tesa, which I know is imperial... back in a moment.
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Back (phew). So, that's graduated 0 - 4 - 0 (thousandths), with each tick representing a tenth. I wonder, therefore, if this is actually a 0 - 40 - 0 gauge, each tick being 0.01mm? Unfortunately, there's not enough of the dial left to be sure either way...
Maybe the solution here is to invent a new measure; let's base it on the average size of a gnat's reproductive member.... so graduate the dial 0-4-0, where each tick represents 0.1gc (gnat's cock) - so long as I can achieve an accuracy of "within a gnat's cock", I'll be happy

As a side bonus, then it doesn't matter if it's metric or imperial!