Can you post a link because numus and Prussia don't really go together (there are quite a few centuries and quite a few hundred km separating these terms).
Numus is version of Prussian Schilling for 1664-1665, etc. Schrötter# 1921,1922 https://www.ma-shops.de/loebbers/item.php?id=221010196 Before, it was the page for this coin in Numista. Now there is not any information.