Actually it is a Goodyear built FG-1D donated back to the United States from the El Salvador Air Force in 1969. See the blurb near the bottom of the More Info Link.
The Chance Vought F4U Corsair was an American fighter aircraft that saw service in World War II and the Korean War (and in isolated local conflicts). Goodyear-built Corsairs were designated FG and Brewster-built aircraft F3A. The Corsair served in some air forces until the 1960s, following the longest production run of any piston-engined fighter in history (1940 - 1953). During World War II, it was the fighter the Japanese feared the most. The US Navy counted the average kill-rate as for every F4U shot down, 11 enemy aircraft were shot down. It had a turbocharged engine, which made a whistling sound when it was in the air. The Japanese nicknamed it "Whistling Death".