Early Color Television
NTSC Prototypes and Field Test Sets
A prototype is defined as a set with a metal-cone CRT, or with screw socket mountings, or with no engraved stamping on the chassis, or which would have been made in very small quantities, or has characteristics/circuit additions that would indicate it is an experimental/prototype set.
Field Test Sets
Most of the sets below were receivers used in "Field Testing" of the NTSC Standards from late 1951 until May 1953. The NTSC submitted its petition after this testing to the FCC in July 1953.
(RCA prototype photos courtesy of Dave Abramson)