Help identifying a tool?

[Farmer J.]

It looks like some kind of mechanism to indicate how far something is wound around something..! It does remind me of the depth indicator on a deep mine cable winding drum, so as the operator can tell how deep the cage is lowered down the shaft. Like this one, the numbers and letters are not evenly spaced. Sorry I don't have my own photo but this link should show the dial:

https://www.jhluxton.com/Industrial-Archaeology/Mines-of-Devon-Cornwall/Levant-Mine/i-8Hfjhq9/A

 

[The Tool Tyrant]

It is definitely a 'Hamster Wheel Dynamometer'...chain loops around a sprocket on the wheel and numbers indicate 'braking hamsterpower'.