I am trying to confirm if the below coin is what I think it is (namely, this coin: https://en.numista.com/catalogue/pieces34989.html):


Its diameter is 22 mm. I can't accurately weigh it because it is inside a plastic card.
If it is authentic, it has been counterstamped with a "21" on the obverse. Some of the grainy texture on the reverse comes from the plastic encapsulation and not from the coin.
If y'all could tell me what you think about its authenticity, grade, and value, I'd greatly appreciate it.
john