Delta-Homecraft hand powered disc (disk) sander. Disk is 8 1/2 inches in diameter, common 9" discs or standard sanding sheets are easily trimmed to fit. Includes the original documentation. Also included is a Delta miter fence that I started to modify to fit the sander.
Mounted on a steel base, it's heavy enough to stay put for light work, or it can be clamped if you want to apply more pressure. Really handy for doing precise work.
The handle could be replaced with a pulley to motorize the sander.
Alberti Design makes a hand-powered sander like this ($1100 + shipping + tax). There's an article on the web by a guy who used a sander just like this one to imitate the Alberti. Search "Hand Crank Disc Sander Creation, Restoration, and Modification" for a write-up, pics, and a U2B video.