It's the 75" Hamilton Standard 6501A-0. It was used for many aircraft including the F4U Corsair and F6F Hellcat. Usually confused with the 6507A-0 that was identical but made of different alloy. The 6501A-0 was made of the HS-26 (HSP-26) alloy while the 6507A-0 of the AMS-4130 one. According to the list of the props, governors and blades from 1963 the prop blade type was used for the Douglas C-54 Skymaster aircraft series with the R-2000 engine and prop assy/hub blade 23E50-473 or 505.