I have 3 hand held meters: Gossen LunaSix 3, Pentax spot and Minolta Autometer IIIF. Oddly, since it is the newest and has a digital readout, the Minolta reads about a stop higher than the other 2, or the in-camera meters in my Nikons. No idea why, and I don't know if it is calabratable.
I was disappointed, I bought the Minolta to be a modern, accurate meter that took widely available batteries, and it appears way out of calibration. Maybe it was dropped before I bought it?
The Gossen reads the same for incident and reflective off a grey card, the Minolta does not.
Craig the likely outcome of dropping the meter it breaks and no longer works. In the big picture it's not uncommon for meters to read a stop apart. I don't know the Minolta Autometer.....but apparently there's a screw under the battery compartment cover.... or ask someone at The Camera Store or Gary at LensmedicYYC to calibrate it for you.