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I am not an expert in this precise series but the coin has the look of a Numismatic Forgery, in my opinion. I have seen many similar Forgeries and this one has that "look".
Based on the location of shadows - there appear to be three raised line segments that do not belong on this coin which could be copied damage from the host.
First a diagonal line between the right top of the W in BRAUNSCHWEIG to the dentil arc.
Second a diagonal line segment from the right top of the N in LUN.
Third a pair of parallel raised line segments above William's eye.
In addition there are numerous raised dots seen typically on transferred images. They appear randomly.
Then there is the rather poor definition of the details. In particular in the coat of arms and fine hair lines. The lettering also lacks sharp crisp transitions at field level.
Perhaps the key is the possible sharp seam line between the faces and the edge of the die.
Toning looks like a non-silver white metal which would fit a lower density alloy and the need to enlarge the diameter and/or thickness slightly to add weight.
As an authenticator I would suggest that there are more points of concern with this coin than there are points that would lead me to believe it is genuine.
My book on Counterfeit Portrait 8Rs is available from Amazon http://ccfgo.com/TheUnrealReales
or from me directly if you want it signed.