Even the uncirculated coins have neumismatic value, are touted by the mint as bullion coins, are legal tender, and are a little cheaper than the proofs.
I guess there is a mint monopoly, but those sales are on record somewhere, too. (Registration predates confiscation, historically).
It was my understanding that even during the 'gold grab' of the '30s, collectors were allowed to keep their coins. If not, I know of one collector, now deceased, who was responsible for increasing my interest in coin collecting substantially by showing me gold coins in my youth (after having sworn me to secrecy--an oath I have yet to break) and gold certificates, which were retained despite the law.
I would have given my right arm for his collection, but was far away when he died and his widow sold the collection before I could return. (I hope she got a reasonable amount for it.)
Frankly, I think he started collecting to dodge confiscation and then got the 'bug'.
In recent decades people have put a seemingly inordinate amount of trust in the banking system, in the transfer of electrons and computer databases.
I do not share that trust.
The system is complicated, and is some ways fragile, and hard copy and hard coin will carry the day if it ever collapses.
That lack of trust is not new.
I had a friend who worked as security in a bingo hall, (pretty large jackpots) and he said there was one little old lady who used to come in on Saturdays with a few red seal silver certificates or United States Notes (rarely an early Federal Reserve Note) and spend them to play bingo. The one he showed me had the paper clip rust stain on it. (The crew promptly 'redeemed' them for an equal denomination in FRNs).
The note had probably been stuffed in a box or mattress, because they did not trust banks. That from the days when banks did collapse, and people lost their assets on deposit.
Unlike the paper money, if they had just tossed quarters in the box or half dollars, they would have had a hoard of silver coins in relatively good shape, one which could have been sold for multiples of its face value. The notes were not in great condition, appeared well circulated for the most part, and would likely not have commanded such a premium as the coins might have.
As a collector, FDR excluded numismatics (also jewelry, service, cookware, fillings, & etc.) from his confiscation laws, giving the wealthy insiders their escape hatch. That is not to say that future “emergency” confiscations will provide the same exclusion. The thugs well armed agents could come home to home for anything of monetary value to sustain the overlords’ opulent lifestyle, all “for the children” of course.