3N could be the keyway of the key – the bit of information locksmiths have to know to have the flexibility to duplicate the key. The “CS” is probably a clue to the door at Evans in Newark that the important thing controlled. However, there are published and non-published key codes. Some code numbers are published in books for locksmith use. Some aren’t printed in these books, so you’ll be able to’t get them from a locksmith. Keys with unpublished codes can solely be obtained from the producer with written authorization from the proprietor of the key, as famous in the manufacturer’s records.