Except for the outside earth screw terminal the old connector looks remarkably similar to that used in Continental Europe well into the 1970s. Originally intended for hot appliances like hotplates, irons, toasters, heaters,... it was used for virtually anything, particularly vacuum cleaners but also floor polishers and a load of other appliances (I think I've even seen an oscilloscope with such a connector). 5mm pin diameter, pin spacing 20mm.
