Having a Centennial medallion on a machine doesn't necessarily mean it's actually a centennial machine. Dealers used to remove the medallion from beat-up machines and put them on cleaner machines to add value. Much of the value in vintage Singers is related to condition (the more pristine, the higher the price). A beat-up Centennial could sell for less than the same model in pristine condition.
Featherweight prices depend a lot on where you live. They tend to be less expensive on the East Coast because of the density of population. In the Midwest, where I live, the top price even for a Centennial would be around $350 now. They could be more expensive in Wyoming simply because there aren't as many in that area of the country. For me, $410 is way too expensive for a machine without attachments and without a case in good condition (you didn't mention a carrying case for it).
Last edited by Prism99; 09-26-2012 at 06:56 PM.