I'm looking through a coin book on spanish coins, unfortunately it only shows the year 1600+, but all 8 reales coins from 1600-1700 appear to be made in 0.9306 silver
Looks like Beldar Conehead's back in town........ Sorry Jankovsky. Couldn't resist being devilish........
I'm pretty sure the Seville 8 reales VIII is it from 1628. Could be a fake, but that is awfully worn to be a fake. Or if it is a fake, it could still be a very old fake from that time. A lot of the coin is missing which is common as parts were cut off to adhere to the weight. Fake or not, silver or not, I'd still take it to someone who might be able to tell you more.
Found some more http://www.todocoleccion.net/felipe-ii-8-reales-s-f-1556-1598-sevilla~x23604864 That one is actually attributed and authentic FELIPE II, 8 REALES, S/F. (1556-1598) SEVILLA More Pics: http://www.rhinocoins.com/spain/fil2g.html
I was being sarcastic. If you looked at my other replies I actually took the time to research the coin and provide him with the ACTUAL coin. Regardless of it being real or not at least he knows what he has or what he has a replica of.
Really, you guys are hopefully pulling our leg. This is a fake shipwreck piece of 8 coin. The one you showed is sold at trinket shops all over the Caribbean. This is one of mine that looks a little like yours, but "real-er." The one in the picture above is like the ones I buy my kids and throw into the pool or the back yard to get them into coins. Hope this helps.
Tigervet ... I can't believe the number of people there that completely ignored (I hope) the fact that it was magnetic. You could see from the very first picture that they were cheap copies.