Maher sent us this picture of a nice 1801 8 reales silver coin from Mexico. It looks great and in excellent condition. Most of these coins have much more wear than this one.
Unfortunately, this coin is counterfeit. It is a good counterfeit, but a counterfeit nevertheless. Counterfeit coins are worth zero.
Our normal appraisal page for these old coins appears at this link. They are quite valuable when in good condition. I hope you have a real one, not a fake.
Most of the time, but not always, it is possible to detect counterfeit coins by comparing them side-by-side with genuine coins. Sometimes well-financed crooks produce excellent copies of rare coins and sell them to unwary buyers for very high prices. Professional authentication services are the only sure way to tell if your coin is genuine or counterfeit. Use PCGS, NGC, ICG, or ANACS for this purpose (look them up on the Internet; do not use other services).
In Maher's case, a careful side-by-side comparison reveals small differences between the genuine and counterfeit coins. Look closely. They are a good match, but not exactly.