If the industry could have started with a 21" CRT, believe me, they would have started with a 21" CRT.
Here's a link to RCA's color TV proposal to the FCC.
https://worldradiohistory.com/Archiv...posal-1953.pdf
Tricolor kinescopes and associated components start on page 263
Tricolor kinescope demonstration in March/April '50 on page 277
Envelope sized pages 296, 297, 322
Receivers for the RCA color TV system page 306.
I have no idea if this will help you or not.