It used to be that paper currency was backed by gold and silver for its value. A 10$ paper note would be redeemable for 10$ worth of gold or silver following the gold or silver standard. Currently our bills are fiat money which means they are not backed by any tangible item. They’re just based on the strength of the economy. The economy can fluctuate so it makes the actual value of a bill unstable. These Mcdonalds coins, however, would be a currency that are redeemable for a Big Mac. This would make them a technically more stable currency as they are always have the value of a Big Mac they can be redeemed for.
Item: Wallet of Infinite Toppings (Basic) once per hour this wallet can be opened to produce a slice of American cheese, two slices of tomato, and a few leaves of iceberg lettuce. In seedy taverns it is whispered amongst the old men of a Wallet of Infinite Toppings (Deluxe) that includes nicer cheese options, bacon, onions, and your choice of sauce…or so the legend goes