I have two of them. I calibrated my film to one of them. The other is off by 1/3 of a stop. But it's just as linear as the other. So when I made a zone dial for the second one I just shifted it by 1/3 of a stop. Now both meters give me the same exposure even if they are slightly off on the internal EV unit display.

Remember if you only have one meter it doesn't really matter if it's truly accurate. You just need it consistent and you can adjust your film speeds. But I tested the meters against the spot meters in my Nikons with simple lenses. It's a good way to get a rough idea if the meter is correct.