Yes, at first glance the year confuses some metal detectorists or readers. But since these silver groschen were Prussian coins anyway, they continued to be minted - parallel to the Pfennigs and the Reichsmarkt that we all know. It is assumed that this was done in the beginning because of a lack of new coins, but also because it was "silver" and the "money in circulation" was kept stable. Also in people's minds, because a new currency had to be accepted.