One Thousand Ways to Make Money by Page Fox

682. THE UNALTERABLE CHECK.--Invent a small, flat leather case with lock

and key, into which the check or checks will securely fit. Only the signer of the check and the officer of the bank have the key. The latter, after paying the check, holds the case for the depositor. This would make it impossible for the check to be raised, or, if lost, for a dishonest finder to have it cashed, as he would be unable to give either the name or the amount. The cases should be made very cheap so that a depositor could possess a number at a trivial cost.