I just posted photos of the exact same model, in much better condition.
In the Jalopnik tradition, I shall call this a "nice price or crack pipe" evaluation.
This seller has smoked the contents of a den of iniquity and is working on a second one as we speak, clearly. Seriously. $40 for that example? Not a chance in hell. One, best case you're looking at really terrible linear or rubber dome. Two, good luck getting keycaps - they have the stem (which is also the actuating element) plus two stabilizing latches even on the 1x1s. Three, it's beat to hell so almost certainly doesn't work. Four, that's not "used" that's "thrown down a flight of stairs and then beaten with a hammer for good measure."
This is what an LK-201AA in decent physical condition, decades of dirt, and some yellowing looks like (with a keycap removed for illustrative purposes.)
