In our industry that's usually made by Skidmore/Wilhelm
And called a Skidmore....
Its easy to check a wrenches calibration
fix the drive in a vise. set the wrench to 10#.... hang a 10#weight 1' from center.. nudge the wrench it it clicks.. you're good.. you can do numerous iterations. 20# ... nd on..
use beam wrenches for critical things...