June Avance was preparing for an upcoming garage sale Wednesday morning when, on a whim, she decided to look at the contents of her husband’s locker from Vietnam.

Among the old Polaroid photographs and other mementos she found what she described as a “fat bullet.” Public safety officials are now trying to determine if the “fat bullet” is a live artillery shell.

A Red River Army Depot bomb expert took a look at the shell Wednesday afternoon and said it was most likely a 40mm practice round shell from a helicopter and probably not dangerous. A bomb expert from Barksdale A...