Starting at the beginning of lunch service on August 2, you can get a limited edition MacCoin when you buy a Big Mac from McDonald's. On August 3 and going through the end of 2018, you can trade that MacCoin back in for a free Big Mac. Or you can keep it as a collectible.
There will only be 6.2 million MacCoins distributed around the world, and they will have five different designs. If you're into the collectible aspect, you'll want to try and find all five. Each of the five designs represents one of the decades in which the Big Mac has been sold since this entire event is celebrating the Big Mac's 50th anniversary.
The five designs start with a classic Big Mac in the center and feature pop culture and artistic nods to each decade along the edges. The 70s coin has flower power, the 80s coin alludes to pop art, the 90s has bold, abstract imagery (think Saved by the Bell), the 00s represent the cloud, computers, and other technology that grew during that time, and the coin representing our current decade showcases the power of communication (so... emojis).
Most McDonald's will be participating, but some might not get very many coins to distribute. Some might not get any at all. This is a global celebration, and McDonald's said only 14,000 stores are participating. There are more than 14,000 in the U.S. alone.