Some people may recognize these rings as "trench art", made famous by military personnel who created art out of metal. They were originally made by tapping the edge of a coin with a spoon to a desired width and then drilling out the center. The method is also said to originate from drifters or learned in prison.
I first learned this method from my uncle who was staying with us at the time. I think I was 4-5 years old. I was taught to do it with a spoon, tapping the coin while rolling it on a piece of wood. I was very young, and I wouldn't properly make one until years later when I was about 16. It was made with a Benjamin Franklin half dollar, which my dad convinced me to give to him and he still wears. That particular ring took me almost a month to make.
Nowadays, I work with a small jewelers hammer and an anvil to make the rings. I use pre-1964 U.S. coins, mostly quarters and half dollars. Depending on the intended size, a single ring can take 6-8 hours to complete, or longer if it is a bigger coin. I mainly source the coins online through eBay.