Intact aircraft. It was the one flown in the 1944 Fighter Conference. It is largely original, but there are several modifications:
1) The original rudder pedals were on a bar that pivoted in the center, making it tough to use brakes when the rudder was hard over. A rudder pedal setup from a Bearcat was fitted so the pedals move fore and aft only, making braking MUCH easier.
2) WWII Japanese pilots were physically smaller than many people today. So, the pilot seat was moved some 4 inches aft to accommodate physically larger pilots.
3) Some U.S. instruments were installed. Most were painted like the original Japanese instruments, and the people who fly it know where the needles are supposed to be.
4) There is a modern radio setup, likely as well as ADSB since that became a requirement in 2020.
5) The main gear doors are not original. They work, but the original gear doors are quite complicated shapes and faithful replicas have not yet been made. Perhaps in the future.
About 3 - 4 years back, the Zero went through a complete disassembly down to bare aluminum overhaul, and everything is in very good shape. The control cables and pulleys, the primer / paint are new, and there were a few permanent repairs of things that had gotten some "hangar rash" over the years. The only things that weren't overhauled were the engine and prop because overhaul was not needed at that time. This Zero is in absolutely great shape.
At the time, I was working for Fighter Rebuilders and stripped off the fabric from the elevators, rudder, and ailerons and prepped the surfaces for paint and new fabric. I can tell you the workmanship inside the Zero is generally quite good. Light, but good. Anyone who thinks the Zero was poorly built is just wrong. It isn't the absolute best workmanship I ever saw, but it was solidly made with decent skill. This particular Zero was built by Nakajima, the engine was Nakajima, and the propeller is a Sumitomo (which is a license-built Hamilton-Standard).
The Planes of Fame website says our Zero was completed in May 1943. From the available monthly Nakajima production data I can find, I think it was completed in Oct 1943, especially since the prototype A6M5 Model 52 supposedly first flew in Jun 1943. Zero No. 61-120 was the 2,357th aircraft of its type to come off the Nakajima production line and was first assigned to the Japanese Naval Air Corps on the home island of Honshu. In a few months, it moved to Iwo Jima, then in March 1944, was reassigned to Asilito Airfield on Saipan. Not too sure where these dates came from. Alternately, the dates shown on the museum website may be correct and the production data I have seen leading me to think it was built in Oct 1943 might be wrong. Since I have no primary reference production data, that well might be the case.
On June 18, 1944, U.S. Marines captured Asilito Airfield with a number of intact Zero fighters. A dozen of these intact Zeros were shipped to NAS North Island, San Diego, California, USA for evaluation. Four Zeros were restored to flight, two went to the Army Air Force and two were retained by the Navy.
The Museum's Zero No. 61-120 was ferried to NAS Patuxent River, Maryland on August 23, 1944 and subsequently flown by about 25 different USN, USMC, Royal Navy and civilian fighter and test pilots, including Charles A. Lindbergh (1944 Fighter Conference). The aircraft was ferried back to San Diego on January 11, 1945, where frontline combat pilots were also given a chance to check out the Zero. Altogether, Zero No. 61-120 logged over 190 hr of flight time in the USA before being declared surplus after the war.
Zero No. 61-120 wound up being sold for scrap, but Mr. Ed Maloney obtained it in 1951 for his Air Museum in Claremont, CA, which opened in 1957.
The Museum began restoring the Zero to flying condition in 1973 and after 4½ years it flew again on June 28, 1978.