UPDATE FOR 2020
My list of most-wanted vacuums for 2020:
Kirby 3C and/or 4C
Kirby 505
Kirby 510
Kirby 513, 514 and/or 515
Kirby 516 and/or 517
Kirby Dual Sanitronic 50
Kirby Janitronic
American Lincoln Super-Sweep (Irish green, 1969-1972)
American Lincoln Super-Sweep (Army green, 1972-1979)
American Lincoln Super-Sweep 180 (white/blue, 1979-1982)
Kirby COMVAC CV1300
Royal 311 Heavy Duty Commercial (series F / 4.5 amp)
Royal 606 Heavy Duty Commercial (series H or I / 5.4 amp)
Royal 608 Heavy Duty Commercial (series G or H / 5.4 amp)
Royal 611 Heavy Duty Commercial (series I / 5.4 amp)
Royal 618 Heavy Duty Commercial
Royal 620 Heavy Duty Commercial
Royal 660 Heavy Duty Commercial
Royal 662 Heavy Duty Commercial
Royal 680 Heavy Duty Commercial
Royal 682 Heavy Duty Commercial
Royal 888 Prestige (series F or G / 5.4 amp)
Electro-Hygiene 980 (series F or G / 5.4 amp)
Galaxie Prestige 990 (series F or G / 5.4 amp)
~Ben