1805 Spanish 8 Reales Coin

It looks fine to me as well, can you post a huge picture of the edge ?
That's what the forgers usually get wrong.
Here are some more details about the coin and date you have : http://www.coinfactswiki.com/wiki/M..._TH_8_reales

Can you also post a clear picture of the date ?
If you have an overdate (the engraved modified a die from the previous year for 1805) - then your coin worth much more than the "normal" 1805.

Here is a link to a "regular" one (without overdate) so you get an idea of the price (which greatly depends on details on the coin and dings / marks on it / wether it have been cleaned or not) :
http://cgi.ebay.com/8-Reales-plata-...em4602957ba3

Copy paste for proper weight :

An eight-real coin nominally weighed 550.209 Spanish grains, which is 423.900 troy/avoirdupois grains (0.883125 troy ounces or 27.468 grams), 0.93055 fine: so contained 0.821791 troy ounces (25.561 g) or 394.460 grains fine silver. Its weight and purity varied significantly between mints and over the centuries. In contrast, the Coinage Act of 1792 specified that the U.S. dollar would contain 371 4/16 grain (24.1 g) pure or 416 grain (27.0 g) standard silver. This specification was based on the average weight of a random selection of worn Spanish dollars which Hamilton caused to be weighed at the Treasury.

Under 26.5 grams, you can start to worry :)

Your 8 reales is better than mine:) Nice coin!