A very rare type of coin in the form of a forgery / copy.
Interestingly, looking at the style, made in the same workshop as the Sobieski offered two items earlier.
At the eagle's paw there is a visible trace of scratching/cutting, perhaps to mar the punch present there (as on item 4359).
Correctly executed serrations on the wound.
White, non-magnetic metal only superficially silvered/bleached, diameter 33.5 mm, weight 16.58 g.