I did calibration on mine once, I decided to ditch the 1.35v baterries and went with 1.5v + recalibration.
1 of the potentiometers seems to handle the minimum threshold for light sensitivity and the second one lets you fine-tune it. Cant remember which is which but can be easily figured out.
Just choose a battery type, then meter an opaque wall(brick)? at, f3.5;1/30 -> and then going up +1stop changing fstop
and then again from f3.5;1/30 -> f3.5;1/500. (always corroborating with a trust-able avg meter.
My Yashica meters precisely like my spot meter, dslrs and slrs under normal circumstances (no backlight sun/snow/sand).