Old Mexican Coin - Please Help - What

you have a Mexican 8 reales, minted in Durango, Mexico. Can't tell if it is real from the picture, you need to weigh it and get Swamperbob to give it his blessing, but 1834 is a scarce date for that mint and has overdate varieties so check it carefully.
WD1040, there were 14 mints in Mexico that produced these coins. Collecing a nice example from all the mints makes a nice collection.
You have a wonderful coin that traded in the USA as legal tender until 1857, nice addition to anyone's collection.

If you look at the date very carefully under magnification, can you see the top of a 3 and the bottom of a 3 under the 4 in the date? That date has a known overdate. Nice find. Please post pictures of the "pieces of 8" you found, I would love to see them.

"8R" is the denomination, 8 reales. The nickname for the 8 reales coin, "peso" became the official name in 1870.

"Do" indicates the Durango mint. This mint operated from 1825 to 1895.

"R.M." are the initials of Ramon Mascarenas, mint assayer between 1830 and 1848.

"10 Ds. 20 Gs." refers to the purity of the silver and equals .903 fine. For comparison, sterling is .925 and pre-1965 U.S. silver coins are .900 fine.

There was no record kept of the number of 8 reales coins minted in Durango in 1834. The mint records only give the total value of silver coined that year.

The official weight of your coin is 27.07 grams, giving it an actual silver weight of 0.786 ounces.