[Arran]

There is a bit of B.S in that pamphlet with regard to "C" batteries, without that bleeder resistor connected across them the "C" battery will pretty much live out it's shelf life as there is next to no current draw. I don't know how many farm radios actually used this bleeder resistor as it's not rare to find a very old "C" battery sitting in the back of the cabinet whilst the "A" and "B" batteries are long gone. In some later 2 volt tube sets they used Mallory button cells to supply the tube bias, whilst in others they used a self biasing arrangement, usually with a resistor network in the "B-" circuitry. But then again this pamphlet was for marketing, which is probably why they do not mention powers a 2 volt tube set from a rechargeable wet cell.
That being said I don't think that the Air Cells were all that popular, if that thread is anything to go by, as surviving examples seem to be few and far between. I'm guessing that the cases must have been molded from hard rubber unlike the typical dry cells.
Regards
Arran