Is it illegal to have antique money? Most importantly they would get at least 3 times more from a collector.
No, it is not illegal to have antique money. In fact, what they were trying to do was perfectly legal, at least in the United States. Though, like you said, they could have gotten way more than face value from a collector.
The bankers had reason to call the cops, though. The only reason someone would try to change in antique money like that is if it is stolen. An intelligent person, who got this money through legal means, would try to sell it to a collector for more than face value.