Old thread, I know. But since I couldn't find anything concrete on the matter I thought I would share my experiences here.
The two pots that Rick mentioned are indeed for calibrating the meter. Remove the rubber bungs with a needle or similar. As seen from the base of the meter, battery compartment facing bottom, the left pot is for the low light range (red) and the right hand pot is for the high range (green).
Both get more sensitive when adjusted clockwise. Mine gave one stop under-exposure in both high and low ranges. Adjusting each pot a fraction of a turn clockwise did the trick.
I tested pointing towards a grey rather uniform cloudy sky, a middle grey card facing a diffused window (meter facing away from window in other words), and an indoor white wall under a combination of tungsten and diffused natural light.
It is a good idea to test if both ranges are calibrated with respect to each other. For instance set to 20 degrees and ISO 400, f5.6 and 1/125s can be read on both scales.
RF: Leica M4-2 | Royal 35-M | Polaroid 110A/600SE hybrid
VF: DIY 4x5 | DIY 6x17 | Voigtländer Vito CL | Foth Derby | Welta Weltix | Smena Symbol | Lomo'Instax
SLR: Canon EF | Pentacon SIX | Pentax SP1000 | Pentax SV
TLR: Rolleiflex 2.8E3 | DUO TLR
CSC: Fuji X-E1
Pinhole: 6x17 Vermeer | ONDU 6x6 | DIY 4x5 | DIY 6x24
Silver Halides - Pictures in B&W