Had a quick look at my Avon, it is a hybrid whether an early crossover from the 17-37 range or a bespoke unit someone commissioned.
Five speeds: 2650, 2000, 1300, 750 and 450 RPM. Motor: Brook Crompton single phase, 550W, 5.1 A, 1425 RPM. Serial Number A830408. Spindle 3/4" x 16 Thd. Bed 48"...