Well, I don't know about being an "expert" on cob coins,

but here's my input.
It sure looks like a Spanish Mexico 8 reales - the only legible writing is the "M" mintmark and "8" denomination mark. I think I can make out the mintmaster's mark below the "M" - it looks more like a J than any of the other possible letters (D, P, G, L, R, or F). That would lock it down to the period 1706-1723. The actual date would normally be found about where the top clasp touches the coin, and the name of the king at the time would be found where the bottom clasps touch the coin - without these, it's impossible to date the coin any more accurately.
Is it genuine? That I can't say. As has been mentioned, these have been copied a lot, though a modern American-made copy should have "COPY" on it somewhere. I'd have thought a Disney copy would have "(c) Disney" on it somewhere, too. They seem to put that on all their stuff...

You could try weighing it - the coin itself should weigh about 27 grams; if the total item (with chain and loop) doesn't come up heavier than this, be suspicious. Still, even that's no guarantee. Some reproduction "pieces of eight" have been struck from real silver, even "real pirate silver" ingots retrieved from wrecks.
If genuine, examples of this coin where the date is unknowable are worth around $90, according to the Krause catalogue. Your coin is mounted, which will damage the coin and reduce the value to a collector, but it looks like whoever put that lop around it has gone to some effort not to damage the coin
too much.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis