From stamps to coins to baseball cards, people collect rare or unique items, at least partly in the hope they will appreciate in value and perhaps one day fetch a handsome sum. One stunning example is the postage stamp collection of Robert H. Cunliffe, which was auctioned off last year by Spink Shreves Galleries.
The collection featured rare postage stamps with an inverted center, meaning the central image was mistakenly printed upside down. In a typical auction, these would be the most expensive on display, if there were any at all.
Click ahead to some of the rare stamps put to auction and the prices they sold for.
Updated: Oct. 18, 2010
Originally published June 18 2009