It looks like a Spanish Reale of some denomination. Carolus III is on the obverse and part of what is probably "Hispania" is on the reverse. Someone with more knowledge on the series can probably help more.
I think this is it: http://www.ngccoin.com/price-guide/world/spain-8-reales-km-4322-1788-1803-cuid-8140-duid-29008 and per this site, a 1800 one would be 150.00 in VG8 or 450.00 in VF20. That being said, your coin is holed so it has it's value drop considerably. Current melt value is 14.42 per this page, so I'd say the value is somewhere between about 14.42 and 50.00.... and probably on the lower side. But I'm not an expert on this one.
Unles that is one humongous hole in there, I don't think that it's an 8 real or maybe not even a 4 real. What size (dia) is your coin? Like a nickel, quarter, half or dollar? It's also an 1806, since they weren't made in 1800.
How big is that coin? It is for sure a Charles III (Carolus III in latin) Spanish Silver reale coin of some denomination. A half reale is slightly smaller than a dime, a one reale is the size of a nickel, a two reale is slightly bigger than a quarter, a four reale is slightly bigger than a half dollar, and an eight reale is the size of a silver dollar
It is from the reign of Carlos IIII. One of the "I's" appears feint. Also, it may be the photo but from the wear it looks as if the last number on the date is a 6 instead of a 0.
I would pay no more than $4-$5 for it. Still, It is a very nice coin with tons of history connected to it. Did you know that before 1857 a lot of the silver coins used in America were actually Spanish Reale coins. Even when these "piller coins" were done being made worn examples were still heavily used in America. The government ordered all of the foreign coins used in America to be turned into the mint to be melted in 1857, in exchange, you would get brand new American coins. The 8 reales was used to be what the American dollars was based on. Also, most of the silver coins found at archaeological early American settlements are Spanish Silver. Anyways, It is a very nice coin, regardless of it's condition. You probably know this, but it is a Half Reale.