Historically, a very interesting piece. Dietrich Uhlhorn developed a modern minting press in the early 1800s and presses of his design were sold into many countries around the world.
I am not at all familiar with this piece nor how to authenticate with certainty.
That said, I think the weight and diameter are acceptable. As this coin proclaims itself a test of the Uhlhorn presses it should be struck rather than cast. For that reason I do have some concern about the extra metal visible within the square hole. However, review of several other examples of these coins reveals some of them also have some amount of extra metal in the square.
Hopefully an expert on this particular piece or series will chime in, but if not I would certainly recommend submitting this to PCGS or NGC for certification.