It would depend on condition or price of the bike it's attached too. My favorite are the Suntour Cyclone and the Superbe. In the Italian line I'd say Campagnolo Nuovo Record or Super Record are very sought after. There's so many nice ones it's hard to say. The Huret Jubilee is gorgeous and they don't go cheap on eBay.Just curious... is there any value in vintage derailleurs? I mean, if you see one on a bike in a thrift shop, is it worth picking up?