It's not exactly pennies from heaven, but McDonald's is planning to make it rain coins to celebrate the Big Mac's 50th anniversary.

Starting at the lunch rush on Thursday, customers can receive a MacCoin with the purchase of a Big Mac at 14,000 participating restaurants across the United States, McDonald's announced Sunday.

And what's the coin good for? Another Big Mac.

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Customers can redeem the new currency for a free Big Mac starting Friday and running throughout the rest of 2018.

In an Interview with USA TODAY, McDonald's CEO Steve Easterbrook explained Thursday was selected as the release date for the brass-colored coins because it would've been the 100th birthday of Jim Delligatti, a McDonald's franchisee in western Pennsylvania who invented the Big Mac.

The coin idea sprung from the role that the Big Mac has played in measuring purchasing power.

In 1986, The Economist started using the Big Mac Index as a way of measuring the purchasing power of international currency. "They use it to this day," Easterbrook said. "Why not have some fun with it? Create our own currency."

The Big Mac has become an American icon over its 50-year run. In 2007, the Big Mac Museum Restaurant was established in North Huntingdon, Pennsylvania, to honor the juicy burger. Its Big Mac sculpture is 14 feet tall and 12 feet in diameter.

And in 2016, McDonald's division in the United Kingdom auctioned off a 740-milliliter bottle of sauce used in the burger for roughly $95,000 on eBay.

McDonald's sold 1.3 billion Big Macs last year, according to the chain.

MacCoins will feature five unique designs, each representing a decade of the Big Mac. The highlights:

•The '70s: Showcasing the decade's flower power

•The '80s: Alluding to pop art

•The '90s: Defined by bold, abstract shapes

•The early '00s: Specifically focusing on the technology that was at the forefront of the turn of the century

•The '10s: MacCoin calling attention to the evolution of communication

Follow USA TODAY intern Ben Tobin on Twitter: @TobinBen