I removed the key-switch from the rear panel of my 4808 and removed the cylinder. I don't advise you do this at home children - that part of the calibrator was not designed for easy maintenance. The local "lock-smith" said they couldn't make a key, but did manage to find a blank that fitted. It took me about an hour to with a fine file to make a key that worked. So if anyone needs a calibration key for a 4800 I can get it copied at the lock-smiths (no I won't make them by hand like the first one - life is too short :) ). Cheers Dave