A Vietnam-era patrol boat that was used by the Armed Forces of Malta for decades before returning to the United States has been added to the National Register of Historic Places, the San Diego Union Tribune has reported.

The 51-foot long Swift boat joins three other museum ships on the register, which identifies buildings, sites and objects considered worthy of preservation because of their historic and cultural significance.

The vessel, named C24 and later P24 by the AFM, spent many years in Maltese service, and was eventually retired in 2012. It was handed over to the Maritime Museum of San Diego, where it was restored. Today it is used for 75-minute tours around San Diego bay, bringing back many memories for Vietnam war veterans.

The P24’s sister vessel, the P23, is still displayed at the AFM Maritime Squadron’s Haywharf base.

That particular vessel had been at the centre of a horrible tragedy in 1984, when an explosion took place while illegal fireworks were being disposed of at sea. Five soldiers and two police officers were killed. Another soldier, the only survivor, was severely injured. The C23, as it was named then, was repaired and went back into service as the P23. It was decommissioned in 2010.

The P23 and P24 spent more than 40 years in AFM service.

They were donated to Malta by the US in 1971, after having been used to train military personnel for the Vietnam War.

“Swift boats, so-named because of their speed and agility, were adapted from Gulf of Mexico oil-rig vessels and used during the war to patrol the Vietnamese coastline, intercepting supplies headed to the Viet Cong and North Vietnamese Army,” the San Diego Union Tribune said.

“They also went up and down the rivers and canals of the Mekong Delta for troop extractions and other special operations. About 3,600 men served on swift boats during the war, including John Kerry, the former senator and U.S. secretary of state, who received a Silver Star for his actions on board one in 1969.”

The P24, now formally known as PCF 816 (patrol craft fast), never went to Vietnam, having been used in the States during the war before coming to Malta.

“PCF 816 is a tangible reminder of the service and dedication of so many swift boat sailors and allows visitors the opportunity to better understand what they sacrificed,” said Kevin Sheehan, the museum’s librarian and manager of collections.

The other vessels on the National Register of Historic Places are the Star of India, launched in 1863 and now the world’s oldest active sailing ship; the Berkeley, an 1898 steam ferry that spent 60 years operating in San Francisco Bay; and the Pilot, built in 1914 in San Diego and now the oldest active pilot boat in the country.