On some other threads it has been pointed out that overstrikes were sometimes not errors, but were an intentional practice to recycle/re-purpose coins.
That is certainly the case with this coin, but I thought I would post it here anyhow.
The Duchy of Warsaw was created in 1807 as part of a treaty between Napoleon and the defeated King of Prussia. Set up as a semi-autonomous state ruled by Duke Friedrich Augustus of Saxony, they coined various denominations in copper, billon and silver (1,3,5,10 groszy, thalers and fractions) between 1810 and 1815.
The Warsaw 5 groszy coin was struck on old Prussian 1/24 thaler coins. I had hoped to see more vestiges of the earlier coin when I got the coin in hand, but they are faint (a bit more can be seen with the coi nilluminated at an angle). Also, the planchet seems none to happy with the additional strike

Attached image compares my photos of the Warsaw coin with images of the 1783 Prussian coin I downloaded from the auction house from who I bought it. My arrows link up the details that can be seen
