AC2, well, another guess might be that it either served or was planned to serve in a metric unit, and has since been repainted in USN colors. Wikipedia reports the British flew F6F-5 off the HMS Indomitable, part of the British Pacific Fleet. Also, reported there is that the French used these in Indochina after the war. Uruguay flew these into the 1960's. My guess now is that someone found this bird in South America, bought it and brought it back for restoration.
Which museum is it at? Expect they would know, or we could put the question to the National Naval Aviation Museum - expect they know the serial number and could look up its history. I once had a question about a Hellcat on the Yorktown in Charleston - its got the -3 rear windows and paint scheme, -5 cowling and windscreen. The answer I got back was that officially, its a -5, according to its serial number and records. Probably started down the production line as a -3 just as the -5 parts started arriving - a 'transitional -5,' so to speak.
I see Hellcats listed in San Diego, Chino, Camarillo and Palm Springs.
-- Checking the Chino museum's site, there's no Hellcat there.
-- The Palm Springs Hellcat has no history posted.
-- The San Diego Hellcat never flew in combat, was always in US service, used in post-war testing.
http://sandiegoairandspace.org/colle...-f6f-3-hellcat
-- On to CAF-SoCal (Camarillo) - if you were looking at Minsi III, then the story may be even simpler - its just a mixed bag of parts from anything and everything, including F4U brakes -
https://www.cafsocal.com/our-aircraf...n-f6f-hellcat/ (the link is good, though they did misspell Grumman in the URL!) Wish the write-up included the history between the end of the war and how it ended up in Minnesota.
So, if it's Minsi III at CAF-SoCal - bag o' parts is the answer.
If its the Palm Springs Hellcat, or another Hellcat somewhere else that I've missed, let me know - expect we can put question to the museum where its at, or ask the National Naval Aviation Museum.
Thanks for asking question - I've had fun doing the research. Maybe someone else can add to this.