It’s inside this metal box.
Great thanks! Looking online, I can see that when opening one of these CRTs there are two green boards on the left and right of a brown board that some people mod to add a service button to. Is that metal box on the “back” of the main brown board, so it would have to be completely removed to work on it? I assume that, that metal box is solder in place or is it folded metal tabs. It looks like it might be a bit of a pain to remove the metal box lid to get at the battery.