I am the fellow who wrote the book "Counterfeit Portrait Eight-Reales
The coin is Counterfeit in my opinion but one that is interesting and should not be passed off too quickly as a recently made Numismatic Forgery. A forgery is basically worthless but a counterfeit is not. How much it is worth varies based on the method of manufacture.
I am particularly intrigued by the edge and what I think I may see.
The design of the coin is completely correct because it was obviously copied from a genuine coin. The edge design is wrong. The method of how the faces were copied is interesting. Did you notice the many round raised metal lumps on the surface? Under the 1 in the date, above the 7 near the edge of the bust, on the crossbar of the A in Carolus, on the reverse on the stop between the mint mark and denomination, on the stop between the FM assayer initials, on top of the I the N and the D in IND etc., etc.
This could be some form of early electrotype.
I believe it is worth researching further.
You indicate you bought it from a dealer who would take a return. Would you be willing to "return" it to me for the same amount? As long as the price is in the correct range I certainly would love to document it.
My book on Counterfeit Portrait 8Rs is available from Amazon http://ccfgo.com/TheUnrealReales
or from me directly if you want it signed.