Oldest coin to date and first silver...MAYBE. Help!

[groundbeeper]

I was Digging today and got a weak signal... lowered the disc until I could locate it. Once the plug was out I found the following coin.
PROBLEM... After a semi-clean up, I discover the 1829 date. After researching this coin, it should be a 8 Reale Mexican .903 silver coin.
8r*P*1829* O.R.*10D*20G is what I could make out on the coin.
The funny part is I can not find that date, at that mint, with O.R. as the Assayer. All I could find with that date was the initials J.S.
I did an at home silver test and from what I can tell it is silver. Ice cube melts immediately and coin gets cold super fast.
Any help and/or suggestions as where to find info would greatly be appreciated

 

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[eyemustdigtreasure]

that coin HAS to have a (special) history attached to it - found in Tenn....?! Wow!!
Great Find!

 

[eyemustdigtreasure]

that coin HAS to have a (special) history attached to it - found in Tenn....?! Wow!!
Great Find!

 

[cudamark]

The color looks like it would be copper. You've scraped and edge and it's silver? Maybe a vintage counterfeit?

 

[coinsareawesome]

No, the copper-y color on the front is probably corrosion. The coin is an 1829 Mexican 8 Reales. They were minted in silver. The P that you see on there is the mint mark. You can't see it, but there was originally an I visible next to the P, making the mint mark Pi. More info... 18/032-1893 Mexico 8 Reales KM 377.12 Prices & Values | NGC

 

[groundbeeper]

No, the copper-y color on the front is probably corrosion. The coin is an 1829 Mexican 8 Reales. They were minted in silver. The P that you see on there is the mint mark. You can't see it, but there was originally an I visible next to the P, making the mint mark Pi. More info... 18/032-1893 Mexico 8 Reales KM 377.12 Prices & Values | NGC

Thanks for the response. Here is what I am wondering. If the coin is not counterfeit... Why are the assayers initials O.R, rather than J.S. which are on all other coins that I can find from that mint for that year.
I was thinking it could be a counterfeit from maybe 1860s time frame when the assayer's initials were R.O. I say from the 1860's because I found it at about 6-7 in. depth, around the same depth and area I am finding Civil war bullets,
As far as the green... not sure if it was from the copper content or corrosion from length of time and soil conditions in the ground.
This really has me scratching my head

 

[coinsareawesome]

There were quite a few of those initials on coins from different years. I honestly don't know why there is an O.R. The two initials from that year are JS and Sc.