I had a Electrolux 303 (70s cylinder) which said Electrux on the bottom also (rating plate) yet i've also seen the name in 50s instruction manuals for lux cleaners, I can only presume its some kinda company shorthand lol.
I'm so glad someone else has seen the 'Electrux' spelling. I'm not going mad! I had an ZA60 with that spelling - see the pic below, and notice that the whole word 'Electrux' is on one line on the badge. On the Electrolux badges, 'Electro' was on top, and 'Lux' was on a second line beneath it...wierd!