I must be the lucky one, I have used the same stick gauge for more years then I can remember, not even sure where I got it. It matches the reading that my truck gives me on the tires almost to the psi . It also is about 3 psi different then my TST 507 readings on my fifth wheel ,so close enough for me . Matter of fact I have had it so long the numbers are wearing off.
To the OP , some of the suggestions seem reasonable. As said I would see if that new one matches up with a tire shop. I recently had new tires replaced on my fifth wheel, and told them what I wanted for air pressure ,and that old gauge of mine was accurate with theirs. How about your truck or trailer monitoring systems any of your gauges match up with them ?