Hello jfransch,
Nice counterfeit. The contemporary copies of Guadalajara coins are in fact scarce because Ga was a low production mint. There are only 5 varieties listed in Riddell and of those only two versions are seen regularly. I own only 19 Ga counterfeits and of that number 4 are duplicates of Riddell listed coins. There is one elusive Riddell that I have never seen. Counterfeiters typically targeted examples from high output mints especially those mints who were NOT using hubbed dies. These copies passed easier - the designs and mint marks were familiar and the variation in the mint dies made minor variations seem possible. That is why Zacatecas is the most commonly forged coin. The originals are crude themselves (strike and planchet problems) so a forger could get away with a lot more.
From the picture, I would guess that the coin is a white metal casting made from a transfer die. That is consistent with the weight, color and the spongy detail I see here. It looks like pot metal. The die matrix (design and element placement) matches the real 1835 Ga so a real coin was probably used as a host to make the molds. The loss of detail in the transfer process points toward a poorly done electrotype or a simple plaster mold. The grain in the casting material could not be too fine or the details would copy better.
The hole certainly looks like a cancellation mark based on placement and this coin may have been retained as an example of a class of forgery that was very common at one time.
The date for the coin is likely to be in the 20th century. This combination of metal and casting method is most often seen on silver coins dating in the 1900 to 1940 era. Pot metal castings were made in huge numbers in the depression era. They are at the bottom of the price scale.
But I am intrigued by a question. Why make such a poor copy of an 1835 Ga 8R? It is too obvious to be a "Numismatic" counterfeit and not heavy enough to pass in a culture that was used to the weight of silver. Perhaps it was a "filler" in a bag of 8Rs that were being transferred in bulk for silver value. This by the way is still being done!
Who knows why for sure, but it is still an interesting coin to speculate about.