A repunched date occurs when the date or digits of the date are fully or partially punched in or around the date itself. Repunched dates are usually referred to as RPD's.
During the 19th century, the date was punched into the working die as the final step in its production. The working die was first annealed to soften it, then the engraver took a steel rod with the raised image of all four digits of the date on it, placed it into the working die and struck the metal rod with a mallet. Sometimes the engraver struck the date punch several times into the working die, to get a deeper impression. If the engraver made a mistake, such as making two images of the date in the working die, he might use an abrasive and remove the unwanted images.