The weird credit card case is now explained.
I went to "the Google" and looked up the name of the business on the letterhead. It was a company who supplies products for pets.
We had purchased heart worm medication for our two dogs and this was the form of the rebate. Lee peeled back the sticker covering the amount and each card is worth $5.00.
The letter states we can use them anywhere they are accepted.
Maybe we can use them at the vet's