actual incident with my credit card

I was signing the receipt for my credit card purchase when the clerk noticed that I had never signed my name on the back of the
credit card. She informed me that she would not complete the transaction unless the card was signed. When I asked why, she
explained that it was necessary to compare the signature on the credit card with the signature I just signed on the receipt. So I
signed the credit card in front of her. She carefully compared (even put on her glasses) that signature to the one I signed on
the receipt. As luck would have it, they matched.