I've never seen them in the wild either (since I had them as a kid). Every one I've purchased has been online. I don't collect HW outside of comics related stuff, specifically marvel, but I easily could see myself getting hooked, as I had them as a kid, so the nostalgia element is there.
The Marx trikes are 1960s I believe? Those are cool, but my self imposed date restrictions prohibit it (pretty much bronze only). Otherwise I'd have shipping containers full of this stuff.
Never heard of tin litho, are they signs?