HUO could either mean low plays and cared for, or beaten to a pulp and just as bad or worse than a routed machine--I've observed both sides of the spectrum on this. But typically, when a pinhead is saying something is HUO, usually it's generally in good shape with maybe some cabinet fade, playfield wear in certain spots, or other minor issues.

CQ would either be a flawless original or a high quality restoration that was flawless and could be considered museum quality. Although, I'm sure some folks would debate about the finer points of this--original parts vs NOS parts vs reproduction parts, and original vs restored/repainted artwork. In general, CQ is simply an exceptional example that wouldn't otherwise be found out in the wild.