I got a very similar unit for $16 + $8 delivery from "Discount Tommy" on eBay. These things are usually termed "Corona" mills (mine is a "Victoria"), but they all have "500" stamped on the side, and they all appear to originate in the same factory somewhere in Latin America, where this hunk o' iron is distributed & sold pretty widely.
Mine works, although I did some tinkering before I ever tried to use it. I commend you to this thread, which will give you a lot of good tips on using this mill:
Toward the end of this thread, I posted some pix of my milling setup.