In 1938, a wallet manufacturer in Lockport, N.Y., decided to include sample Social Security cards in its products. The company’s vice president thought it would be clever to use the actual Social Security number of his secretary, Hilda Whitcher.

It wasn’t. The sample card was half-size, printed in red, and bore the word SPECIMEN in large letters, but by 1943 more than 5,000 people were using Whitcher’s number as their own. The Social Security Administration voided the card and started a publicity campaign to educate users, but over the years more than 40,000 people reported the number as their own, some as recently as 1977.

“They started using the number,” Whitcher marveled. “They thought it was their own. I can’t understand how people can be so stupid. I can’t understand that.”