Hemingway Authentication Scheme
From 1955, intended as humor:
In the future when I should ever call on the telephone to make a request or issue an order I will identify myself as follows: This is Hemingway, Ernest M. Hemingway speaking and my serial number is 0-363. That is an easy number to remember and is not the correct one which a con man might have. A con character would say 364. So we will make it 363. Any character can then ask how many shares I own and I will reply truly to the best of my knowledge. If the bank has made any once contemplated mergers or there has been a split that I had not been informed of I might give an inaccurate answer.