I am looking at a Zenith parts list for the "S-50364 "1000" Series Stratosphere Transmitter Assembly".
Along with it are parts lists for the 300 and 400 series transmitters.
Only the "1000" references "Stratosphere". Also most of it's parts have numbers newer than the 300 and 400. This is from Zenith Service Manual SP-8 (1961)
HERE WE GO!!!
This was for a home theater!!!!
You could switch to the radio or phono and even
change records.
John of Memphis