The US Mint sells $1 coins on its website, doesn’t charge for shipping, and takes credit cards.
It’s an opportunity for free miles: buy coins, deposit those coins back into your back account, use the money to pay off the credit card. Net result = the miles for the charges on your card.
Here’s the Flyertalk discussion. Reports are consistent that these show up on your credit card statement as purchases rather than cash advances (fortunately!).
These are ‘Presidential Dollar Coins’ and there are only (6) different ones out so far. They’re adding another 2 per year, apparently. And unfortunately you’re limited to purchasing 500 of each. So right now you can buy 6 x 500 = $3000 and thus 3000 miles.
Not quite as lucrative as the days when you could buy savings bonds on your credit card, or prepaid gift cards that operated as debit cards and could be used to purchase money orders redepositable into your account ($3000 worth a month back around 2003-2004).
But it’s a little bit of effort and some free miles, so some will find the strategy useful.