Use it as-is. They use the elastic bending of the beam to measure torque. They won’t really get out of calibration unless you over-bend the beam or mess up the pointer. Calibration is done by changing the length of the pointer.
I have one just like it. The only issue with them is seeing the scale when you’re in an awkward position.


Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.