Book value with no toning would put this coin around $280, so it sold for 1.65x guide. That is a fair price for it. I would have been surprised by anything under $400.
It's a great looking Type coin that has everything going for it , high grade , FSBs , and some beautiful toning . Coins this nice will always command a premium and are well worth it when found . It would be a perfect coin with a little earlier date from the '30s .