I don't really know about other chassis, except that most of my older sets look maybe just OK, but my CTC-4 luminance section probably couldn't be more "sharp", or provide a more excellent picture. Chroma is also very good, but narrow band, as most know. Perhaps just a lucky circumstance, or maybe an extra measure of diligence to provide decent pics to encourage sales.
My 4 also has a correct gamut CRT, before the "gray screen" tubes. Best viewed in a totally dark basement LOL.
Kevin