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).
Harrison 15-inch (also badged as the 190) with a full screwcutting gearbox
A rare version of the 15-inch with a simpler, 3-lever screwcutting and feeds gearbox