Our Late '50 PAF's use alnico IV, this, subtly change the character of the humbucker, to sound soft, sweet, but with body. There isn't many details of the magnets that  gibson used in this first period from 56 to 61, but apparently used all alnico II,  IV and V, but alnico II is associated with paf 57, and alnico IV is associated with the sound of Mark Knopfler and his Les Paul 59 . The materials used for this set are: 42 AWG plain enamel copper wire, alnico IV magnets, nickel silver cover and plate (brass free), keeper bar for the steel screws and maple wood spacer. As an option, the winding can be between 7 and 9 kOhmns. Also, the output cable can be made of one wire with shielded push back wire, or of four wires and ground to have the split coil option.