If you use a meter, any meter, and shoot some chrome with it, the results will tell immediately tell you if the meter is reading somewhat "correctly" (assuming the camera is in the ballpark)
Reading a spot meter in and of itself is a bit subjective, as is the exposure that one might choose from the readings. One can easily use any meter, calibrated or not, so long as its roughly correct and so long as one is familiar with the meter and camera. It's the desired exposure that one is after. How that is arrived at is less important.
Most modern meters don't need calibration to be close enough. How you use the meter, and how you interpret the results is a vastly larger variable that is only mitigated with experience with a specific regimen and the results thereof.
A day of testing handily trumps an infinite amount of calibrations.