RGB is the highest quality of broadcast image, but it is functionally indistinguishable from YPbPr, which is very common on late model CRTs, even ones that are entirely non-progressive (i.e. 480i & 240p). Given that set is from 1986, it is likely to have been used much more than a set made in the year 2003, or so. Driving to work today I saw a KV-32FS100 on the sidewalk, looked like it was in great condition but I let it stay. I have no interest in acquiring more non-HD CRTs at this point, as I have a few already, but I would put a bet on that thing on the sidewalk having a better image than the one this guy is trying to shill for the better part of a Benjamin.
Personally, I'd not even consider a CRT that old unless it were for novelty's sake. Like an old console with wood paneling, etc. It's just way too likely to be dim or more worn than a newer tube. But if I were as hard up as you seem to think you are I would still not purchase that one if I couldn't test it out in person first. Can you not drive around town in a bad neighbourhood or anything? It's these kinds of places that I see old televisions the most. One particular street I drive through on my way to work frequently has folks dumping piles of the things. When they sit there long enough or get piled so high the kids come along and throw rocks at them to break the glass, but I've rescued at least three from that street. One of them even got rained on the day I picked it up and it still works like a champ.