The Bureau of Engraving and Printing sells them through the official government website, priced above face value as collectibles. Every note can be cut out and spent. Handing the whole sheet to a cashier is also valid, though they will silently curse you.
Credit: JFitz717
Looked at doing that to get miles but it’s considered a cash advance and there’s a fee.
No that was the thing, it was a purchase not a cash advance. Most importantly there was free shipping on the coins. So what people were doing was buying the coins with their CC then depositing the coins in the bank to pay off the bill, thereby getting you free miles from your card, at no expense to you.
I believe the reason this promotion existed was an attempt by the government to get the dollar coins into circulation, but ended up being cobra effect situation because then the banks were just sending the coins back.