One tube regenerative radio
I believe this little breadboard radio to be a kit. The knob on the little variometer and that on the variable cap are of the same style. I have seen similar kit sets in the Allied catalogs of the late 1930s. The tube is a type 31. When I first located this, all of the components including pencil-marked Fahnestock clips were mounted on the plywood board with small wood screws and were ready to be wired. No wiring or solder had ever been applied. I had to repair the variometer as the Double Cotton Cover insulation on the wires of the movable coil had deteriorated. I wired the set with DCC wire according to the generic diagram shown and was able to make it work surprisingly well with a pair of "D" cells for the "A" supply and 5 rather worn 9 volt batteries in series for the "B" supply. Assuming this was indeed a kit, let me know if you can identify the distributor.
I have been told this kit was part of an early NRI (National Radio Institute) course. If you have evidence in the form of a diagram or printed material, please let me know.
The circuit has been positively identified as from NRI. Al, N2ZHS and Lou deGonzague of the Antique Radio Club of Schenectady identified the kit as from an early 1930s version of NRI's course. Here is a picture of a page in the course. If you have the full lesson related to the kit, please send me an e-mail. Let's make the information available.