Keystoker boiler, best offer.http://harrisburg.craigslist.org/grd/5626524813.html
Looks like it's a K-6. From the photos it's hard to tell if it has 3 grates or 4. Comes with an extra stoker. If your looking for a coal stoker boiler, you could likely get this one for a couple hundred bucks, maybe less. It's ugly and rusty but I doubt if anything is really wrong with it.
If you go to look at it, first check that the DHW coil area isn't rusted out. That is the one thing that would kill it for me. The only other things that could be wrong with it are the hopper and the stoker, easy to fix or replace those parts.