...as long as you stay clear of silver dollars, which are getting to be very widely counterfeited.
First go to a long-standing and legitimate dealer. While that in itself is not a foolproof guarantee, they usually have relatively inexpensive equipment which can test the basic authenticity of gold and silver coins with an immediate read-out, and also show you what fakes look like. They should be happy to show that to you.
Man, you should look around as to fake Morgans & Peace dols. There are CITY BLOCKS in China with SEVERAL companies devoted to counterfeiting US SDs.
On ebay, they are widely sold by clearly Chinese companies; typically stamped “REPLICA”...for $2-3. One has to ask “what happens when they delete the REPLICA stamp?
In some sense, “loose” “circ’ed” SDs are a bit more detectable, provided you have looked at great numbers of them. I have about 200 junk SDs and have looked at them plenty but you could probably tell me 15 teeny details about them that I don’t know if you were the super expert. There are several distinct wear patterns....but there are few varieties that wear quite like “O” mint dollars. The coining machines used in the New Orleans mint were all used, in some cases, highly used, and “O” strikes are almost always “not so good”. Most people think that an “O” mint marks are rare. In truth, most of them are not. ‘92/’93/’94/’95 are the rare ones.
WIDELY sold are “CC” mint mark SDs because they command such high prices. In counterfeit slabs. Yes, in counterfeit slabs.
I am 98% non-numismatic when it comes to junk, by the way. I *AM* aware of very low mintage SDs. On silver dollars, as you probably know, while they were made for maybe 50 years with up to 5 mint marks, there are really only about 15-20 rare ones.