I'm not certain it is fake either. Take a look at the link in the Op. It shows both sides, but I did not see the weight.
Thanks, Bing. I didn't see that link. Authenticity aside, it appears to have been set in a pronged bezel at some point in its life-- rather aggressively!
I based my fake diagnosis on that hideous picture of the misshapen edge and how odd the reverse looked too. Didn't realize this was a former jewelry piece, which might account for that. The poster on that site also says the coin is not his, but someone offered it to him for 500 Euros, but he didn't think the coin was worth that much. He also said he was not convinced by the style and fabric of the coin, or the source it came from, about the authenticity of it as these are often faked.