Lost key?

The JCMs are rare now. You can't get keys cut for registers, so you really need to find a dealer. Sometimes you can find keys in another brand that have the same lock. I think some models were similar to some samsungs or Towa models. If you can't find a JCM supplier in your area, try ringing some suppliers of other brands and see if they have any similar keys.
Your other option is to take the lock apart and remove the tumbler pins from inside so that it can be turned by any key.

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If anyone is looking for JCM gold manuals, c-tech has one of the best resources e.g G105, G211, G215, G223, G225, G356, G375, G381, G556, G585, J3500E.
These manuals can be found here:

http://the-checkout-tech.com/manuals/cashregisters/jcm1.php

Registerman
August 2010