Okay, I am back. Thanks to y'all helping me and encouraging me, and Googling things you mentioned, I was a lot smarter when I went this time!
I scanned them, and we weighed them. All three seem to be false, but I will explain why I think so, for your review. Last things first.
After I carefully scanned them, I mentioned that one good thing to do is to weigh them. He said he had a good scale, and went down to the store and came back with the prettiest tiny digital scale, much like the druggies use on TV.

(

?) I want one.
1846 Seated Dollar. 18.8 grams.
1800 Bust dollar 19.6 grams.
1799 Bust dollar 20.2 grams.
Amorgan said: a Morgan dollar should be about 26.7 grams...
As best as I can dig via Google, the lightest silver dollar, badly worn, should be more than 22 grams, and as best as I can tell most silver dollar designs when new weighed much closer to that 26.7 grams. None of these showed more than minimal wear.
I did not have a magnet. If I can find one, maybe I will run that test when I go back. Hey, we should have some on the refrigerator, no?
I explained to him when I asked to scan them that there many thieves in the world, and 'experts' (well, I think you are and I am typing this posting) said the Chinese were making false coins, and it was possible his father had been swindled (my Spanish is poor, so I said robbed) by a crook when he bought them.
I think I will walk downtown to buy the ham my wife wants, and see if he wants to do the magnet test. Thanks a zilliion. Better he get bad news than I have legal problems.
This passes the buck to others so he doesn't think I am blaming him. And, as someone suggested, there is no way to assume he knew they were false.
Oh, another thing, though in the form of a question. As I said, thanks to y'all I was much better prepared. I examined the rotation front to back.
All my newer US coins, and the Mexican ones for that matter, if I hold the coin heads up, and aim it so the top is aimed up, then swivel the top of the coin towards my face so I can see the back, the back will then also be aimed up.
That means front and back are made 180 degrees off. Not sure if I am explaining that right.
One of the three, the 1800, was probably within 5 or 10 degrees from a true 180, but the other two were off about 20 or 30 degrees from 180.
Would one not expect the front and back to be aligned at 180 degrees? Is that another sign of a bad coin or they made them that way in those days?
If someone wants to examine false coins, I can post the six scannings, though I may make them smaller since it looks like they are false without further ado. I realize many of you already know what they look like, but if someone doesn't, your wish is my command.
Oh, man, this was interesting! I get all enthused when I am working on a mystery, though I prefer when I actually have a chance to solve it. You guys helping me on this really fired me up.
I am a little sad for him, though. I would have liked to see him come into some money.