The 5-cent card, displaying a picture from inside Carlsbad Caverns, was postmarked Nov. 10, 1958 from Whites City, N.M. and was addressed to Bragg's wife, Sarah, and daughter, Beverly.
Bragg, then a 30-year-old Marine on leave, sent the card to let his family know he had spent the night at a motel in Snyder, Texas, and was sending a package from a souvenir store near the caverns.
A. U.S. Postal Service spokeswoman says the card may have spent years stuck in equipment thought to be empty, but there's no way to be sure.
The couple will celebrate their 57th wedding anniversary in March.