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

Sold for: $260,000
Estimate: $550,000

This multiple ranks as one of the greatest rarities in U.S. philately. That such a multiple exists, particularly being an imprint and plate number multiple of one of the rarest and most popular of all US inverts, is most remarkable.

It is one of only two plate number multiples extant of the Four Cent Pan-American Invert. The other is a bottom-margin partial imprint and plate no. 1145 block of four, with similar centering and traces of original gum. That exceptional block was sold in 1998 and was acquired by Pimco's Chief Investment Officer Bill Gross, and it is unlikely that multiple will be sold any time soon. The Cunliffe strip of four is equally impressive and is unique as a full imprint and plate number multiple.

Sold for: $47,500
Estimate: $40,000-$50,000

This is the only recorded example of this stunning error, and it is one of three Beer Stamps to be found with an inverted center (each of the three is unique). This one, which was once in the collection of Edgar L. Green, was the first of the three to be recognized.

Because there has been no public sale of a Beer Stamp Invert and due to their unique status, it is difficult to determine the market price. There is only one other United States Inverted Center that is unique. When that stamp made its last appearance at auction, it realized $120,000.

Sold for: $130,000
Estimate: $67,500

As with many famed inverted centers, the story as to how the errors came about and were placed into circulation is an integral part of investors' fascination. This famous rarity of Belgium — the only inverted center stamp of the country — is no exception. The stamps went on sale August 5, 1920, as planned.

Several other customers purchased the 65c stamps and affixed them to letters. Then Hye de Crom purchased one of the Termonde stamps. He noticed that the Town Hall was upside down. Knowing the potential value of these major errors, de Crom returned to the window to buy more stamps from the sheet. He succeeded in purchasing 16 inverts in all.

Sold for: $60,000
Estimate: $20,000

The attractive Arch of the Hall of Classics design used on the dollar values of the Junk series was printed in sheets of 50 (10x5) in the Peking printings. Only one sheet of 50 stamps contained this error when it was found in the Hankow post office. This is the sole plate number single from the sheet.

Sold for: $100,000
Estimate: $25,000

This stamp is a mint example of the rarest of the Third Issue Inverts. It has full original gum, better centering than most of the existing copies, lovely rich colors, and is in “very fine” condition.

It is arguably the most desirable Two Dollar Fifty Cent Inverted Center of the mere fifteen recorded. It is the only mint example with full original gum, and one of only three that are completely sound (the other two sound copies possess similar centering to this). However, as a major condition rarity, it is signed "W.H.C."

Sold for: $55,000
Estimate: $35,000 

The 4 anna "Inverted Head" of India is one of the legendary rarities in 19th-century philately. There are just 27 confirmed examples of this stamp, only three of which are cut square.

The most popular explanation for the square cut is that these errors were discovered very early on and some of the printed albums of the period had illustrations of the error. It is believed that many of these were cut to shape by early collectors to match the space provided in the album.

Sold for: $16,000
Estimate: $30,000

From its last appearance at auction in the Harmers "Inverted Centres" sale of February 25, 1963, it has had expert restoration of a small facial thin within the center oval by the letters "PRO" of "PROTECTORATE." Of the mere fifteen examples of this rarity known to exist, it is still is among the finest, as nearly all have faults much more severe than the Cunliffe example.

Sold for: $85,000
Estimate: $48,000

According to most accounts, this "Inverted Frame" variety was discovered by a local collector at a small village post office in Manchioneal, Jamaica, in 1922. It is presumed that only one sheet of 60 had the error, with half the sheet going to Manchioneal and the other half to Kingston.

An estimated 10 to 20 of the stamps still exist. The phenomenal corner sheet-margin pair offered here is the only recorded pair and ranks among the most important rarities in British Commonwealth philately. It is also one of the premier inverted printings in the world.

Sold for: $170,000
Estimate: $500,000

The 1918 Twenty Four Cent Inverted Jenny is one of the most recognized and desired rarities in all of philately. Its legendary status began the moment the stamp was issued in May 1918, when William T. Robey purchased an entire error sheet of 100 at the New York Avenue Post Office window in Washington D.C., just one day after the stamp was issued.

Within one week, Robey sold the sheet for $15,000 to the well-known Philadelphia stamp dealer Eugene Klein, scoring an impressive return on his initial $24 investment. The whereabouts of at least six examples of this stamp are unknown and presumably lost to philately.

Sold for: $42,500
Estimate: $60,000

The 1866 10k Brown and blue is one of the rarest and most famous stamps of Russia. In addition, it is one of the key highlights for a serious collection of inverted centers of the world, making it one of the stars of the Cunliffe collection. Less than 10 examples are known to exist, and all have been used.