5.25x5.25x1 Magnet sandwiched by two steel plates Magnet is Painted White as shown in the photos We cannot determine type classification of magnet, but it's powerful. Overall size 5 1/4 x 6 3/8 Wide (at flange)x 4 1/2 Tall (at hub center) @19 LBS. Hub is a 1 1/16 Dia. x 2 7/8 Tall steel cylinder supporting a stainless and rubber isolation bushing. It can be removed.
This magnet was pulled from a vintage drive repair facility and was probably a part inside a large tape or hard drive. No manual or peripherals are included. .