Aside from all the questionable 8 Reales of all dates coming from overseas , the 1760 Mexico City Carlos III is a problem coin. It was copied in large numbers over 40 years ago in the U.S.A.. So unlike the copies and fakes from Asia , you are most likely to run into one of these from somebody selling in the U.S.

 The main ways to pick these out:

1, The weight of a correct coin is 27 grams , maybe as much as a gram lost to heavy wear or pitting. Anything less than 26 grams is almost always a fake.

2,The example they copied was a "cracked die" coin. A raised "break" in the field or background next to the righthand globe is easy to see. Real coins with this die break are out there , but they are a very small % of the good coins. Only one die broke like that out of hundreds used.

 3, The edge is not correct. It is a bit hard to describe how it is not right , but a normal 8 reales of that time had a repeated bracket or leaf pattern, {{{{{{{{. The copies are sloppy on the edges.

I hear a number of stories about these coins , one is that they were made to give out at Mardi Gra , another was that they were a promotion for a Pirate movie back in the 1950's. All I can confirm is that they must have been made before 1960  as a lot of people say they "found them in grandpa's cigar box" , or "Played with it as a kid".

 Keep your eyes open!