The work of one of the most famous Polish forgers - Jozef Majnert.
He was a Warsaw medal maker who lived about the time of the Partitions (b. 1813, d. 1879). Working at the Warsaw Mint since 1830, he produced a number of medals, but they were not the ones that "made" his name famous in the numismatic world. What he is mainly remembered for are the counterfeit coins he produced from around 1836 until he lost his position at the Mint in 1851.
To this day, stamps from his forgeries have survived, with tin prints appearing fairly regularly in antiquarian circulation. It is much rarer to find two-sided minting, in silver. Such as the present coin.
It is a Majnert forgery of the crown thaler of John Casimir.
One of those that Majnert did not invent, but used the original numismatics as a base. As we read in Mankowski:
"... This is an art undoubtedly of Majnert's fabrication. Stamps by hammering the casting created, namely the bust side so very shallow that the figure of the king is barely visible in places. The reverse side better successful...".
Silver, diameter 43. mm, weight 29.84 g.