Hi,
The calibration cell simply verifies that the meter is 100
microamps and a total of 250 ohms. And it contains the limit resistors
for the leakage test. I wouldn't worry about it.

Incidentally I wouldn't use any silicone lubricants on the
card-reader pins. While the original organic grease has stiffened with
time and needed to be replaced, it was probably carefully selected to
do its job. On the Cardmatics I've repaired, I've used a grease
originally supplied to General Radio by Oak, but I have no idea where
to get more of it. It was described to me by the GR engineer who gave
me some, as "Beacon M325" grease.

73, Alan