The Talking Machine Forum — For All Antique Phonographs & Recordings

The seller thinks that this came from an early recording studio. If so, how did it work? If not, what was it for?

https://www.ebay.co.uk/itm/VINTAGE-MUSI ... %7Ciid%3A1

Its a starrett speed indicator. It could have been used in a recording studio but certainly not exclusive to the recording industry. It is used to count revolutions of shafts that ran machinery.

https://www.oldtools.co.uk/products/sta ... gLgf_D_BwE

https://www.ebay.co.uk/c/9015608216