1884-CC Authentication And Grade

Looks like a classic chinese counterfeit, and the grainy surfaces and weird "wire" rims suggest that it was cast.

The extra thickness is, of course, a ploy to get the weight up to a deceptive level. Clearly a forgery, and I concur that it's most likely out of China. Estimates I've seen are that there's a million or more genuine specimens of this issue extant in mint state, many still in their GSA packaging. No reason to consider one that looks like this even if it was real.

Edit: I'd add that if you're going to be buying raw silver coins, you'd be well advised to acquire a digital scale, ideally with an accuracy of .01 gram. These are readily available on ebay for less than $10, and if you avoid just one fake using it, it will have more than paid for itself.

Obverse is way off, so is the mintmark, it also has plenty of pitting as is often seen with Chinese counterfeits. This one is a fake.

Chinese counterfeit

I was fairly certain it wasn't authentic, but the guy didn't really want to hear it. I have a digital scale, but I was at the flea market selling when he brought it by to see if I wanted it, so I didn't have it with me. I showed him your responses so that he would see that it just wasn't me being overly cautious. His demeanor when I showed him the evidence seemed odd though. If I had a coin like that that someone proves to me is a fake, I would be fairly bummed. He just thanked me for teaching him how to spot a fake.