Eighty years ago this month, the April 1939 issue of Radio Retailing carried this ad for Sentinel portable sets, featuring the country’s lowest priced battery set, the model 170-BL.  The three-tube superhet sold for $14.95, including battery, and featured a tube lineup of 1N5G, 1N5G, and 1A5G.  Filaments ran off a 1.5 volt A battery, with a 90 volt B battery.