Numismatic is a beautiful word.
It sounds scholarly. It sounds like something a museum curator would say. It sounds, above all, like something worth more than ordinary gold.
That last impression is the point.
Because in retirement account sales, "numismatic" is very rarely used by numismatists. It is used by people who need a reason for a coin to cost far more than the gold inside it.
The short answer to the question is no. Numismatic coins are collectibles, and collectibles are not permitted in an IRA.
The longer answer matters more, because the word gets stretched to cover products that are not really numismatic at all, and that stretching is where retirement accounts get damaged.