Check this out, seemingly it's a Electrolux 504 made out of about 4 different machines from the 500 series, if nothing else it's different.
Ian
[URL unfurl="true"]http://cgi.ebay.co.uk/Vintage-Electrolux-Vaccum-Cleaner-with-bags-working_W0QQitemZ190182480792QQihZ009QQcategoryZ69856QQssPageNameZWDVWQQrdZ1QQcmdZViewItem[/URL]
