The wonderful 1930’s era National SW-3 was one of the first commercial receivers marketed to the Radio Amateurs. There were three main models – an all DC, all AC and a hybrid of the two.
The National SW-3 started advertising in 1931 – and was NEW! in the November QST
What is interesting is that up until the late 20’s, hams built their own gear – there were basically no commercial manufacturers at the beginning. Another interesting thing was that not everyone had AC – some rural areas did not. The third main fact that is interesting is that the SW-3 might have been one of the the last regenerative receivers available – the 1931 QST issues show how the world was moving to superhet designs.