£175 - £200 depending on condition would be fair a price, they can make a little more but being CO2 are not as popular as they once were, Basically the same pistol as the early Air Arms Pro J, not much has changed on the new models other than they are Air, Air Arms sold both versions (Shrouded and Classic as yours was known) Originaly in CO2 and now Air, not sure the classic is still available, IMO the classic was the better looking of the two.