The Hoover 500 appears the same as the Blackstone/Hoover in the USA.
The Hoover 600 in the manual is a slightly revised version of the same machine - plastic control panel instead of aluminium,and added a pressure-switch-operated brake to give a neutral drain till the tub is almost empty. ( Neutral drain is mechanically controlled by its own pressure switch, not by the timer - the only machine on which I have seen such a gadget.)Otherwise the same.
Hoover 700 - plastic outer tub, electric pump, timer gives a neutral drain increment, deleted lint filter.
Hoover 800 - plastic lid and top panel, stainless steel basket, short agitator shaft, cheaper timer.
Hoover 900 - minor cosmetic changes. Last of the Blackstone derived series though almost every component has been changed in some way from the original design.
Chris.