38/38.1 mm is fine. Nobody has gotten it right, though I do appreciate all the guesses! Your next clue is: (everyone can now guess again) This coin is 90% silver
That is incorrect, but thanks for trying! Next clue: There is a stone seat on the obverse image of the coin.
Wow @The Half Dime! happy birthday, and a trivia win!? Congratulations! The answer is Liberty Seated Dollar