The 1844 “44 over 81” Braided Hair Cent (Buy on eBay) is one of many interesting varieties of the series and also one of several date blunders. The date was first punched inverted, especially evident by traces under the 4s of the date. While not rare, this variety is popular and especially in demand in high grades.
An example graded PCGS MS64RB which is tied for the finest known realized a price of $29,900 at an auction held in September 2011.
While variety collecting of this type is not as popular as the early large cents due to the minute difference of dies it still is a very interesting field of study. This variety is also listed in literature as “blundered date”.