I bought this off of, you guessed it, craigslist. This is an indexing head that can be driven by the table of a Bridgeport to create a spiral cut. Outside the rust it is in great shape. There is a missing cover but does not effect its operation. These are used when you don't have a 4 axis CNC. I haven't put it to use but will when needed. Most of these are only used to put a hex head on a piece of round stock.