It's a 2-piece dingus... The inner piece is nearly always there, but the outer piece (photo below) is always missing. Hence as you say, the cord stays on the chassis when you remove the back. And I know why they're always missing! I personally guarantee that you can find this piece rattling around in the bottom of every tube caddy, TV repair tool box, and probably in the ash tray of every TV repair van that was in use between the 1950s and 80s
. If you dig through any TV hardware box, you'll find yourself one. I think the same piece was used from the 50s (as soon as they stopped putting the interlock on the HV cage cover) through the late 70s (change-over to the CTC97-ish modular chassis). Just for the record; I think the one I'm showing on my CTC-9 consolette is installed upside-down.
Charles
