Another case in point, the Hoover model 0 is not the rarest vacuum out there. There are maybe around 10 or so known to exist in todays time, in collectors hands.
How about the even rarer Spangler suction sweeper, or the black/gold/red machine that became the hoover 0, Or the hoover commercial model 0, or model 1, 2 etc. Those in most minds are much rarer than a model 0.