If the nameplate is missing and you don't have a ruler to measure the centre height, the 15-inch Version (Model 190) model can be instantly identified by its long foot-brake, an item missing from the 13-inch (Model 165).
A dedicated manual is available for this range of lathes. Some version had a row of rotary switches arranged in a line across the face of the stand beneath the headstock (as above) while others included a 4-spoke capstan handwheel with various arrangements of switches below and to the side. If your Harrison differs, the writer would be pleased to have photographs.