1/4 Sol from Metz. Fake? [解決]

Hello it's my first time writing down on the forum and I'm an amateur who recently did some research about this coin which seems to be a 1/4 Sol from Metz. The date seems to be either 1689, 1639 or 1659 as it's supposed to be.

Though I think it looks good even if it's in a quite bad shape, it doesn't looks like it's made of silver but rather copper, as the little green rust on it and it's black, maybe even red-ish color seems to indicate.
Maybe it's just because it's quite old and the silver is just oxidized, but I still wonder if it's a real coin made out of silver or rather a fake one as I think. If it does be made out of copper, I wonder if it's a copy made during these time like those false reproduction made under the First French Empire.

I thought about cleaning it to see if it's just due to a quite apparent patina and some copper residue on it, but I'm reluctant to that idea.
Anyway, here are pictures.



(Sorry for the quality)

I hope you'll be able to answer me and thank you for those trying to help me.

(Sorry if some sentences/words sound wrong, strange or mispelled, English is not my primary language.)

I believe you're correct. It does seem to be this coin: https://en.numista.com/catalogue/pieces22062.html
Of the 3 dates only 1659 exist on the page for this coin.
I'm not an expert but even though it's a "silver" coin it's only 11.1% silver. I'm not sure what makes up the other 88.9% but to me it's not surprising it has non-silver corrosion product on it. I wouldn't try to clean it.

Just found a couple of the same type coins on eBay. They don't look too good either.

Thank you for answering rsirian. With such a quite small amount of silver, I guess it can explain the seemingly copper rust and maybe the quite black tone of the coin, probably due to oxidization I guess? There seems to Also be some red-ish spots, maybe those are non-oxidized spots or like iron rust? It's difficult to tell.

Also, about cleaning it, it world reduce its value? Or is it because it may damage it? I tried once to clean a non-valuable coin but it did... Some unexpected results on it.

Copper is a very common alloying element in silver coins. I'm fairly certain a coin with 11.1% silver would have a lot of copper in it and possibly other elements (maybe iron) in it. Over time, especially in a corrosive (wet) environment, the coin will corrode (green from the copper) and possibly reddish from iron. I don't see any reason (unless the diameter and/or the weight is off considerably) to think your coin is fake.
As far as cleaning, I think you'll end up damaging it more than removing the corrosion products.

I hope you can have another go at taking pictures. the first ones are hard to make out at all.

引用する: "Cjfrontennac259"​(Sorry if some sentences/words sound wrong, strange or mispelled, English is not my primary language.)

​Don't worry, there's nothing wrong with your English. Your pictures on the other hand, they really aren't well enough to work with. To me, the last number looks like a 5 in stead of a 9 but that doesn't seem to fit in with the existing dates. Maybe it's a later type (1665 could be a possible date), because your coin hasn't the date in exergue while the picture on the coin page does?