The older type B56 motors have the 5/8" shaft and were widely used up to the 1980's and less frequently since.
Made by Brook Crompton/Gryphon/Newman.
These are available in both Single and 3 Phase up to 2hp.
Typical applications such as lathes, drills, car ramps and lots of extraction fan systems.
Meddings Drills, Myford and Boxford Lathes, Chip Shop extract and equipment, Pumps etc etc.
Various mounts and designs - Drip Proof, TEFV, Resilient Mount.