This varied slightly because they were hand-cut and sometimes the alloy was not precise. The prescribed weight for these was supposed to be a little over 27 grams as made. Potosi mint (Bolivia, known as Upper Peru in Colonial times), denoted by the 'P' to the left of the shield 8 Reales (see the VIII denomination to the right of the shield) Just to confirm the exact attribution of the coin: NOTE: DON'T try to clean it! Leave the patina as is. Value - assuming that in hand it is authentic, somewhere in the area of $100-150 American. It is quite worn (appears to have circulated for quite a long time, which would be pretty typical for a piece used in Central America), and it's obviously holed. I don't think authenticity is a question. lions/castles are normal style for that period, etc. The detail looks fine for assayer 'curved R' (this dates the coin to right around 1602-1613). The speckled toning is a bit odd, but I think that's just due to 'environmental effects' of how/where it was stored. rather, it appears to have come from a reasonably well-protected land-hoard based on the patina. It does not look to be a sea-salvaged coin at all. Your piece is certainly not from the Atocha. As mentioned in a prior post, the paperwork confirming that a coin came from the Atocha (primarily a photo-certificate) is quite important to the value. Because the ship was particularly loaded with silver and gold, the long search to find it became famous and as such, the coins that were salvaged from the Atocha wreck sell (now) for roughly a 2-3 times premium over what normal 'cob' coins of the period sell for. however, the pedigree to THAT particular shipwreck makes an 'Atocha coin' more valuable.

Now, this was the same style as the coins that went down on the Atocha. The Atocha ship, laden with riches from the Spanish colonies in the Americas, met a tragic. These coins were part of a vast collection of silver and gold transported from the New World to Spain during the 17th century. This style of coinage is called a cob, hand-struck on hand-cut planchets the Spanish world calls it 'macuquina'. Atochas, named after the legendary Spanish ship Nuestra Señora de Atocha, are a treasure trove of history and intrigue. The Atocha (short for Nuestra Senora de la Atocha) was simply a ship that wrecked in 1622, not a type of coin. I think you have a misconception of what is meant by 'an Atocha coin'.

Atocha silver coins value