I am surprised as well to find out Gilfillan made TVs. I see Gilfillan radios every now and then on eBay or CL, but this is the first of their televisions (color, yet!) I have ever seen. Since this set is a prototype, however, I'm not surprised. It may have been manufactured in very limited numbers, so this one is probably one of a very few such sets in existence in the United States. It may have been made very shortly after RCA's NTSC color television system was commissioned here, so I would not expect to have found very many of these TVs anywhere.
How could this Gilfillan TV be an original design, when RCA had a corner on color TV production in this country?
It would have had to use inventions of RCA, as no one else was making color TVs at the time (early 1950s). The chassis would almost have to be an early RCA one, such as CTC2 or CTC4.
The CRT should be easy to find, if the original is dead (no emission? Open filaments?). I cannot imagine the 21AXP22 being so rare, even today, however, as to be unobtainable. Worse comes to worst, you could always get one from a junker set, not necessarily RCA; I'm sure other TV manufacturers used round CRTs in their early sets as well until the mid-1960s, when rectangular tubes became popular.
BTW: I had no idea, until I read dieseljeep's post, that Sarkes-Tarzian television tuners were cheap ones. I was under the impression for years that S-T was one of the better makes of tuners. What made them "cheap"? Flimsy designs with cheap plastic parts, underrated components that failed after only a very short time, or . . . ? I can see such tuners being used in cheap 1970s-'90s pre-DTV portables, but good grief, not in high-end sets. After all, I am sure Zenith and other well-known TV manufacturers would not have been caught dead using cheap tuners (or other cheap parts) in their TVs in the '50s.