Many years ago, I picked up an interesting midget radio from the depression era. It had the nameplate Westinghouse, but I couldn't find the model number. When I took out the chassis, the radio had been worked on with many modifications/repairs. Since I couldn't find the model number I took a chance, looked at radio schematics of the 1930's that used the same tubes and worked from there. Got the radio to work but what model was it? After a lot of detective work, I came up with nothing and put the radio aside in hopes that someday I will locate the model. Some 10+ years later, I was selling off radios that I felt weren't worth keeping and this was one of them. I took one more careful look at the cabinet and with the light in the right direction I could barely see a model number punch stamped into the wood on the bottom of the cabinet. I could barely make out WR-21 with the "W" really faint. This confirmed it is a Westinghouse model made in 1935 according the Rider's Perpetual Servicing Notes.This is an early example of AC Transformerless Radio using 5 tubes, a design philosophy that would continue to the end of vacuum tubes as the "All American Five" (AA5) Tube Radio. Problem was that the layout of the radio is the same but tubes did not match the WR-21. It is a 5 Tube Superheterodyne radio using 6A7, 6D6, 75, 42 and 25Z5 vacuum tubes.There was no service notes on any changes like this. The mystery continues. I did more research into the 1936 model year and Westinghouse came out with the WR-100. The WR-100 is a small tombstone style rather than the midget and has a chassis layout a lot different than mine. However it used the same tubes as my radio. After pondering this I took a guess that my WR-21 was a mid year upgrade since tube technology and standardization was rapidly moving. Westinghouse made a design change using the newer tubes and put them in the WR-21 and did not update the service notes. I rewired most of the radio to the WR-100 design. It was difficult and frustrating at times because midget radios have very little room to work with so it was difficult to see if one was making the right connection. After about a week of rewiring and checking over I was done. Then I noticed in the schematic a small button battery was used to bias the grid of the First Amplifier Tube (type 75), which was not on the WR-21 schematic. After some research I found that a battery was sometimes use to bias a tube because it was cheaper to use a battery than a resistor in those days. Since in this application the battery would last for the life of the set which usually wasn't too long since midget radios were generally throwaways. It was a cost effective approach which is the reverse today. Made a 1935 equivalent battery circuit with 2012 parts and positioned it as it might have been in 1935. Turned on the radio and it works! I'm keeping this radio it was worth the wait!