Navy bottlenose dolphins involved in a mine-hunting training exercise off the coast of San Diego found a museum-worthy 19th-century torpedo on the seafloor, military officials said.

The dolphins were working on mine-hunting training exercises in March when they recovered a 130-year-old Howell torpedo — one of the first self-propelled torpedoes developed and used by the U.S. Navy.

“There were only 50 Howell torpedoes made, and we discovered one of the three ever found,” said Braden Duryee, operations supervisor for the SSC Pacific Biosciences Division.

The dolphins, named Ten and Spetz, followed procedure when finding an object of interest: They surfaced and touched the side of a trailing boat. Ten and Spetz actually each discovered the brass-coated torpedo separately, two weeks apart. After the second find, Navy divers went in and recovered it.

Bottlenose dolphins have served in helping the U.S. Navy since the 1960s. The cetaceans are perhaps not the oddest animals trained by a country’s military to serve — the ancient Greeks and Romans used bees as tiny weapons; in ancient India, elephants carrying javelin throwers and archers were used.