Welding Tips and Tricks

I recently picked up a miller model 250 ac/dc welder which from what I can tell is a predecessor to the dialarc 250.
It seems to burn rod just fine on all settings but the ac ocv is lower than expected and the amperage is lower than where
Its marked, is there a way to adjust or correct the scale on it? Best guess on yr. Is 63-64, the date stamp on the rectifier is 63.
When i have some time I was goin to build a secondary box with amperage and voltage meters, the main issue is its throwing me off a little the welder at work burns hotter at the same marked amperage, I end up having to adjust a few times to get it where its burning the same. Any thoughts or suggestions would be appreciated.

I've heard it said many times, different machines behave differently. The amperage dial is a gauge not an instrument (different level of accuracy ).

You could get a clamp-on ammeter, and write the 'real' readings on the dial with a Sharpie. Takes two folks, one to run the arc and one to read the meter. But it's effective, although not particularly elegant.