An extremely rare period forgery to the detriment of the issuer.
Piece caught by issuer, stamped FALSE, and marked with forgery class.
In the upper right corner, probably the inventory number from the archive.
Very rare, we have not encountered a replacement series forgery.
Period forgeries are an extremely interesting area, in the case of Polish banknotes still under investigation and open to many new discoveries. We have no doubt that this forward-looking subject still has a period of increased interest ahead of it.