Ah yes...the hose for my childhood Eureka Super Automatic 260 upright! Indeed, the tool port is on top of the motor hood in front of the headlight. A matching blue plastic Bottom Plate would be snapped onto the metal brush roll cover underneath to seal off the suction and prevent the spinning brush roll from rubbing out the carpet while it stood in one spot when tools were used. Unfortunately, the plastic Bottom Plate could scratch delicate floors if the cleaner was moved on bare floors. But the plate also protected hands and feet and made it safe to grab the upright from the bottom when moving it as you cleaned a flight of carpeted stairs.
This tool conversion set-up was used by Eureka for about 10 years from 1959 to 1969, and was even used on the Eureka Emperor made in Japan by Panasonic.