It is always a question what to collect. Majority of collectors never pass by an interesting phenomenon of the XIX century coinage. The technology became well developed and the coins started to look very similar. The dies worked for many strikes and from time to time were in excellent condition, but the year, written on them passed.
As the result just for rational reasons the dies were used again, and the date only was recut. Thus an new overdate die was born.
This phenomenon was widely spread. In Europe it is hard to name a country, where there were no overdates.
Sometimes these overdates have historical meaning.
For example a recent coin https://www.muenzauktion.info/auction/item.php?id=2945227 shows an overdate of 1831 over 1830, as it is given in the description.
The coins of 1830 are so rare that they are seldom seen on market. Indeed there is KM#Pn95 for the year without any recommendation for price, though prices of $2000.- and more are easily present. Now the simplest way to see the coin is to visit a state collection in a historical museum. In this situation the overdate allows a common collector, to keep in hands a die of rarity, It informs that the coinage of the type in fact started a year earlier. As a bonus it is overdate that gives the opportunity to examine practically original die of a rare 1830 coin and thus helps to avoid counterfeits.
