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RCA's Radiola 100 loud speaker was introduced in Sept. 1925. The disc shaped housing contains a large 12" PM, cone speaker driven by a "horse-shoe" magnet, armature type driver. RCA's advertising boasts loud clear sound through-out the audible range with no distortion.
The model 100 is a typical high impedance, two wire PM speaker which will work well with any on the 1920s Battery or AC radios requiring a two wire PM speaker. I believe it to be one of the best sounding speakers of the 1920s.