Similar to what I posted in another thread:
Carry a box of donuts to a shop and ask to compare your gauges to one or two of their best gauges.
What I do when I have a device that’s off by a known amount, and not practical to adjust, is put on a label with the correction factor.
For instance, I have a pencil gauge I keep in my glove compartment.
I have a label on it (made with a Brother P-Touch) that says “add 2”, so I know to add 2 psi to its reading.
I have a digital gauge (Radio Shack!) that agrees with the TPMS in the car, so I have high confidence in those.
That gauge only comes off the shelf to do comparisons a couple times a year.
Then, most of my tire checking is done with an Accu-Gage dial gauge that has drifted 3 psi over many years of being bumped about.
I could get a tool to pop off and re-seat the needle, but it’s not worth the bother IMHO.