Found a 1978 RCA colortrak console TV

[wa2ise]

RCA, in the early 80's, was using, in production, a kind of magnetic tape that was formed in a ring around the CRT neck. In the factory, they would adjust various magnetic fields thru this tape ring, to do convergence. Once the factory worker felt that this convergence was good, on this particular CRT, the production machine making the convergence fields would "record" these magnetic fields into this magnetic tape, like a tape recorder does to imprint the desired magnetic fields onto tape.

Field repairs would require that the TV repairman throw away this piece of tape, and install a thing that had several adjustable magnetic rings, and adjust them to get convergence. repairs like replacing the yoke, or the CRT.

Don't know if RCA was using the above magnetic tape scheme in 1978.