The 1858/7 Flying Eagle Cent is the only known overdate for the short lived series, and very popular as such. Only the earliest die states show clear remnants of the 7, making those the most valuable.
On lower grade examples or later die states, there are certain die markers which can be used to help identify the variety. These include a triangular chip in the field between the date and eagle and a broken wingtip on the eagle.
The grading services PCGS and NGC have certified around 350 examples of this variety, which would also include a number of resubmissions. Based on the certified population, this variety is scarcer than the much more well known 1856 pattern pieces.