Not Sure What This Is. 1830 Mexicana Silver

Ostensibly an 1830 Mexico City minted "cap & rays" 8 Reales. The weight's not out of line given the apparent wear, but there is a nearly correct weight counterfeit of this exact issue known (Riddell No. 197). Looks as if there's a small break in the top of the "C" in "Mexicana" which might serve as a diagnostic one way or the other. A specific gravity test would likely be in order. It may very well be genuine, but this genre of coinage from this era can be tricky.

A specific gravity test as far as for coins goes
tells you what the coin is basically made out of. I.E.: silver
or other metals etc. There are counterfeits that were made out of silver though. Compared to pics. of other known counterfeits yours
seems to be genuine. Not a big premium on this coin as it is worn pretty well but still cool to own. There are some that even collect
the counterfeit ones.

The 1830 Mo JM is not a counterfeit in my opinion. All die indications are that it is real. The weight is about perfect for the wear and the coin is rather common. I am unaware of any 1830 Mo counterfeit varieties which does not make an error by using a smoothly outlined cap. The odd looking connections to the rays in this case are actually a good marker of originality since Mexico City was noted for making transitions from the edge of the cap to the individual rays. Mints like Guanajuato never made distinct joins like that resulting in may varieties where the rays do not actually contact the cap.

SG testing is actually easy. All you need is an accurate High School level triple or quad balance that has an accuracy to +/- 1/2 percent.