Challenge Coins are a military tradition, which is said to originate at the start of last century. They were distributed based on merit in events or for other reasons, and hold deep personal value.
The BeeWare Challenge Coins are die cast, 4.5cm (1 3/4") in diameter, and are made of a nickel/zinc alloy with enamel highlights.
Any contribution to the BeeWare project earns you a coin.
It doesn't have to be a code contribution: a documentation update counts. A blog post. Helping someone during a sprint with their contribution.
And as an additional incentive, for those people who help others get their challenge coins, we have a second coin: the Yak Herder
Revolution Systems provided the funding for the second pressing of the BeeWare challenge coins.
Github provided the funding for the first pressing of the BeeWare Yak Herder challenge coins.