Read a bit about fakes here, especially the part about the collar: http://drapedbustcoins.reidgold.com/page_7.html The real coin should weigh +or-27 grams...which isn't exactly helpful I know.. http://www.coinfacts.com/silver_dol...rs/1799_silver_dollars/1799_silver_dollar.htm Those are just the first 2 google results I pulled up. I'm sure if you check around more, there are plenty more resources.
The first one (die hard, speaks about it being the same weight and looking very much like the real thing.
@Tyler Graton posted some fine examples with diagnostics, but I can offer a quicker authentication technique: 1) Is it a $1000+ coin if legitimate? 2) Is it in a cardboard 2x2? 3) Is it at a flea market, in a Craigslist ad, on eBay, or an "estate find"? If the answer to all three is "yes", it's a fake. Yes, it's possible a real coin could be lurking in a 2x2, and be offered at a fraction of its value by an unknowing seller. Worry less about missing such an opportunity, and more about being killed by shrapnel from the meteor that's struck by lightning just as it was about to miss your head.
