An Alnico magnet is made from various element combinations for different grades of Alnico. Alnico magnets were developed by G.B. Jonas in 1939 and his patent for Alnico’s is 2,295,082. Cast Alnico is a combination of Aluminum, Nickel, Cobalt, and Iron as a filler. There are around 12 grades of Alnico with both Isotropic and Anisotropic orientation. Alnico magnets are used in the majority of vintage Fender and Gibson pickups. Cobalt Steels such as 36% were used on the ES-150 pickup. Alnico magnets were used because of availability.