One of the most exciting parts of collecting baseball cards is finding printing errors. Sometimes mistakes slip through quality control in the card manufacturing process. These errors create one-of-a-kind cards that are highly sought after by collectors. Their rarity and uniqueness make error cards potentially extremely valuable. Here are some of the most famous and valuable error baseball cards collectors look for:

1909-11 T206 Honus Wagner – It’s no secret that the standard 1909-11 T206 Honus Wagner is the most valuable trading card in existence, but an error variant takes the prize. In the early 2000s, a Miscut Wagner was discoverd that shows portions of another card on the right side. Due to its unprecedented nature, it’s considered the crown jewel of error cards and its value is estimated well above $2 million, shattering records.

1952 Topps Willie Mays – The iconic rookie card of Willie Mays is a legendary issue itself, but an amazing printing plate error took this card to new heights. In 2009, a copy surfaced with “PHOTO OF REFERENCE DO NOT USE FOR PRINTING” printed across the image. As one of one in existence and bearing a message never intended for the final printing, its value reached $500,000 at auction.

1987 Topps Barry Bonds – A hugely valuable early Bonds rookie, but one surfaced with his photo inserted upside down by mistake. The factory did not catch the error and distributed it as is. Today it stands as arguably the most significant post-war error card, regularly topping $100,000 at auction.

1969 Topps Nolan Ryan – Topps is known for off-center cards, but some are more off than others. One 1969 Nolan Ryan rookie achieved immediate fame thanks to a miscut placing Ryan’s image entirely on the right side of the card. It’s a breathtaking error to behold and considered the finest miscut card in existence.

1972 Topps Roberto Clemente – One of the rarest errors from the 1970s involves a Roberto Clemente card found with reverse image/text, essentially a negative. Topps has stated only a handful left the factory that way, so this is truly one of the most elusive errors to find.

1957 Topps Hank Aaron – Topps made mistakes with color variants even in the 1950s. An example is a 1957 Hank Aaron card that was instead printed with the yellow/red color scheme reserved for managers/coaches. Incredibly scarce, less than 10 are known to exist.

1975 Topps George Brett – Issues with color bleed were pretty common for Topps in the 1970s, evidenced by a 1975 George Brett that was accidentally printed with colors extending completely off the card. Errors with the photo itself extending beyond the borders make this a true one-of-a-kind.

2011 ToppsUpdate Bryce Harper – Highly coveted by collectors just a few short years old, this Harper RC showed up miscut so his image is dramatically larger than intended. Examples like this prove errors can happen even with modern issues having stricter quality controls.

1956 Topps Mickey Mantle – Mantle is the undisputed king as far as value for 1950s issues goes. But one 1956 takes the cake – discovered with part of the next card visible, it’s one of the rarest miscuts from that decade, still in pristine condition. It’s worth hundreds of thousands.

1970 Topps Nolan Ryan – Like Brett, issues with inconsistent coloring occurred frequently for Topps in the early ’70s. A 1970 Nolan Ryan shows a gigantic blob of extra color swallowing up the entire left side of the card. With such extensive coloring errors, it stands out as one of the most visually dramatic from that era.

Those represent some of the most famous and valuable baseball card errors collected today. As random mistakes, their uniqueness and rarity make each one hugely desirable among advanced collectors. With strict modern quality controls, errors from recent years are uncommon, making older issues from the early printing era most prized. Even common players can have tremendously valuable errors. Finding and documenting new ones remains part of the thrill of the hobby. With card condition and demand constantly changing values, errors may turn up worth many times their original estimate.