Starting on Monday, McDonald's released more than one million MacCoins at 2,500 restaurants across the Chinese mainland to celebrate the 50th anniversary of its iconic Big Mac.
The collectible coin can be redeemed for one free Big Mac at participating McDonald's restaurants through 2018, the fast-food giant announced on its website.
McDonald says that more than 6.2 million commemorative coins will be distributed in more than 50 countries. There are five different designs for the coin, representing the decades since the launch of the Big Mac.
Customers in China can get a MacCoin by singing a birthday song for the Big Mac at any participating restaurant, although customers in Beijing and Tianjin have to reserve a spot in via WeChat first.
Beijing Youth Daily reported that people are selling single MacCoins online in China for up to 180 yuan (26 U.S. dollars), with a set of all five versions of the coin selling for prices ranging from 500 to 1,000 yuan.