I've bought from KEH for perhaps 20 years and have always found their items to be working, unless stated otherwise, and very conservatively rated. Case in point: I just bought a Pentax LX in their BGN condition. A few barely noticeable scratches on the prism and on the base plate, and a little brassing on the self-timer base, a little dust in the viewfinder, which I blew out. I'd wager most dealers would rate it as E or better. Works perfectly. Talking to Josh at KEH (they're a local call for me) he told me that ALL their items are checked over to make sure they're working.
A sad contrast to a vendor in the northeast who sold me a camera/winder rated E which had a slightly dented prism, heavy scratches on the base plate, missing the coupling plug for the winder AND the rewind switch wouldn't work! As you can imagine it went back, I expect their check for a full refund soon. I'm not likely to deal with them again.