If you follow the keyboard collectors market (yeah, didn't think so . . .) then you'd certainly know that the IBM model M15 split ergonomic is pretty much the most desirable keyboard out there. A small number of them were made over a short span of time (1994-1995), and their clunky plastic knob and super-adjustable design meant that over years many of them broke. So when one lands on eBay, it's a big deal.