Almost Uncirculated Mexico silver 8 reales coin.
Minted at Guanajuato Mint (Go mintmark).
Very Rare overdate variety with 1875/6.
Certified by NGC to AU Details (Rev Scratched).
Dark toned with underlying luster.
Dunigan Go55: "The normal date is common, while the overdates are very rare."
A reverse year (1875/6) overdate is very unusual. Dunigan gives a plausible explanation: "Perhaps at the end of 1875 there was an unexpected demand for more coinage... Assuming the 1875 dies were worn out and the new dies for 1876 were ready, ...took a new die for 1876 and repunched the last digit of the date with a 5."