Corsair Mk I   :Fleet Air Arm designation of F4U-1


                        Corsair Mk II : Fleet Air Arm designation of F4U-1A


                        Corsair Mk III : Fleet Air Arm designation of F3A-1D


                        Corsair Mk IV : Fleet Air Arm designation of FG-1D

Photo Royal Navy Mk Vought Corsair    

Credits to NACA , US National Archives,  US NAVY, USMC, Vought