Since Air-Way invented and patented the disposable cellulose sanitary dust container, no other cleaner would be able to use it. Of course, Hoover tried in 1929, with the launch of their model 725, but Air-Way quickly moved to sue the hell out of them. Stealing another company's patented invention, just because your own machine belches dust, is just an admission that Air-Way did it first, and better.
This is the Indicator from the second version of the Air-Way upright. Again, fairly primitive.
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