Prototype set is here

[Eric H]

Originally Posted by miniman82

The numbers on the horizontal transformer are T-6942 and vertical is 208T9 and 274113.

I believe that last number is a Mfg and Date code, RCA built (274) and 113 would be the 13th week of 1951.
The transformer in your last picture has a 274125 number or mid 1951.

Are these off the shelf RCA parts or were they made specifically for the Prototype?