GE portacolors were probably the last, also they had a
19" , C-2 chassis IIRC that probably was almost as late.
They were used in many store brands & started at $250.
A real toilet IMHO. Zenith ran the 4 tube hybrid til F-line
1975 as a leader 19". They also had a 14" 1/2 tube
chassis that may have sold in G-line but dont remember.
Most ended in 74-76, people didnt want tubes anymore.
73 Zeno