Sparton AC-63

The Sparton model AC-63 (63) was replacing the AC 6-15 Electric (in short AC6) in October 1927 (with the same price). This is according to "Radio Manufacturers of the 1920's", volume 3, page 118. The AC 63 is an AC 62 in drop-front cabinet, with minor chassis changes.

The schematic is common for three models: AC-7, 62 and 63. But only the AC-7 has the two C-171 in parallel, the table models 62 and 63 employ only a single output tube. The circuitry is the same, except for the 2nd tube C-171. The second chassis for the "Transformer & Rectifing Unit" (spelling error in the schematic) is not counted for its tube.
See also the article here about different radio seasons.