The iconic McDonald’s Big Mac burger that has sat atop the multi-billion dollar chain’s drive-thru menu for decades is turning 50 years old. To honor the unofficial king of calories, carbohydrates and cholesterol, McDonald’s wants you to get a limited edition MacCoin.

Beginning at lunchtime Thursday, customers who buy a Big Mac at one of the 14,000 participating locations in the U.S.— including across Michigan — can receive a MacCoin, while supplies last. Starting Friday, you can use that coin to get a free Big Mac. The promotion lasts through the rest of the year.

McDonald’s expects more than 6 million MacCoins will be distributed across the globe. The commemorative coins feature five unique designs, the company said in a release. Each represents a decade of the signature sandwich, incorporating elements from that period of history with nods to art, music and pop culture. The front of the MacCoin celebrates the 50th anniversary of the Big Mac.

  • The ’70s coin highlights the decade’s flower power
  • The ’80s coin alludes to pop art
  • The ’90s is defined with bold, abstract shapes
  • The early 2000s specifically focuses on the technology that was at the forefront of the turn of the century
  • The 2010s MacCoin draws attention to the evolution of communication

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