Not much mate.£30-40? Maybe less. Your best bet is to put it on ebay or gumtree (if they let you) I wouldn't get your hopes up about selling it on here but you never know! Put a pic up if you can it'll help value it more
It will be a Spyder Threaded Barrel.
Spyders run on a blowback system, and the Anti-Chop is a sprung bolt tip rather than eyes or similar - although it's an electronic board, it may not possible to cap it at 20bps.