A little interesting item that is pretty obvious what it does, but there is something unique about it. At least to me it is, since I've never seen one before.
I just never seen or heard of one before, Are you saying yours only goes in one direction?
Handy tool to have, I was fooling around with it today, I found it in customers house, the lady said it was there when she bought the house several years ago.
A vibration tachometer? Hard to tell with the pics, but with those you just hold it onto a motor and it magically tells you what rpm it's at. Never used one and I'm probably wrong. Good luck investigating!
IH Farmall 656 gas/ IH 240 Utility/ 2, Super C Farmalls/ 2, Farmall A's/ Farmall BN/McCormick-Deering OS-6/McCormick-Deering O-4/ '36 Farmall F-12/ 480 Case hoe. '65 Ford 2000 3 cyl., 4 spd. w/3 spd Aux. Trans
I have a couple older, smaller one's with A-C marked on them. These were used to check the cylinder speed on the Allis All Crop combines.