Eurekastar is correct: That is the standard plastic hose and pan converter provided by Eureka for all their classic, fan first, F&G bag, Dial-a-Nap or Rugulator uprights. If I remember correctly, the upright attachment set was Model 60D.
Of course, it may also have been sold with any of the Eureka-made store label clones: Montgomery Ward, JCPenney, Eaton Viking, Baycrest and Beaumark.
Though the set up did capture all the suction generated by the fans in these Eurekas, the major flaw was the foam "weatherstripping" used in the pan converter - after a few years of use, the foam perimeter strip would begin to come loose or disintegrate. Standard foam weatherstripping was always a good replacement!