What is this Scale used for?

Thank you for your time! As someone who sold tools for 25 years, it’s not often I am stumped... this scale not only stumped me, it also stumped the owner of the tool store I ran, as well. It measures approx. 6” x 1 3/8” and is made of stainless steel. The lines curve as we get closer to 0. The back is completely plain. I thank you in advance for your help!

 

Here's the FOXBORO entry on the U.S. Patent & Trademark Office site. It details their areas of business.

https://tmsearch.uspto.gov/bin/showfield?f=doc&state=4803:8edwin.2.13

Debora

 

Foxborough makes pressure and flow measuring systems. This looks like part of one of those. It could have measured the height of a column of water or mercury or something to measure pressure or flow rate. Flow is often measured by using pressure drop across an orifice or other element so that could explain the nonlinear nature of the scale. You can probably find it in one of their catalogs if you dig around.