The Hoover Aero dyne model 50. I had the tank FOREVER and over several years pieced together a complete vacuum. The only attachment I am missing is the upholstery nozzle. They had a permanent dirt bag/collection area that was messy to empty IMHO. I put a generic fit all tank bag and it works fine. Much cleaner to empty. For such a large machine, they didn't have as much suction as say an Electrolux. Hoover got it right with the Constellation though.