Great Vacuum!
I had a carpet cleaning business in the 1970's and used Advance machines. The CarpetTwin vacuum was a terrific machine. It used a cloth shake out bag or disposable paper bags. It had two brush roll sizes if I remember correctly--the 12" or 14" depending on your cleaning needs.
The, "matching", rug shampooer was also a twin motored cleaner. It operated on the dry foam method which as truly the best at that time frame. Steam was not yet being used and the only other option was the wet wash with high powered extraction to follow.
The Advance rug shampooer pumped air into a suds solution creating foam that was forced onto a large brush roll. (Advance had their own brand of shampoo made specially for their shampooers.) A separate motor turned the brush roll that had an alternating tufted soft bristle pattern. The foam was so dry that when you finished the job the carpet was ready to be vacuumed. The, "dry foam", lifted the dirt to the surface. It worked beautifully and left minimal residue.
Thanks for sharing those photos--it brings back memories. I had hoped to find one of those but have pretty much given up hope. They are on ebay occasionally but in pretty beat up condition. Yours is a beauty and a keeper!
Are paper bags still available?