Rand, there are some nice images of rare cards (McKinley, WW25, etc.) in this old thread.
Also a bit of discussion on McKinley card acquisitions . . . Dan's and also a dealer who bought one as part of an entire lot of US Caramel Presidents at a live bankrupcy auction, for $600 (!!) . . . and then turned around and flipped it at the Ft Washington baseball card show for $10k!
http://www.network54.com/Forum/526604/thread/1163198626/The+rest+of+the+story-+McKinley