I found this tool in my Dad's toolbox many years ago.
I've tried to capture the detail of dials.
They are crops of the originals with Sharpening in Picasa 3 - Fuji FinePix SL300
Hand-held rev counter (2) by taffopol, on Flickr
Aperture-priority ƒ/3.1
4.3 mm
1/105
ISO 400
Hand-held rev counter (1) by taffopol, on Flickr
Aperture-priority ƒ/3.1
4.3 mm
1/180
ISO 400