The Checkers are an item that can increase sanity.
The player can exchange this item for 1 water bottle, if given the chance by the randomly occurring trader event.
Cards are a way better to not get insane, Checkers are better for other events (The Ammunation Trader, the Food and Water Trader, etc).
When the checkers taken during scavenging, have a possibility of bringing back food or a radio.
"When we were passing through the ruins of a bar, we ran into a soup vending machine. We couldn't find any spare change, so we decided to pay with checker pieces. It worked!"
"We don't have a lot of opportunities for entertainment these days. So when we saw a big, mutated snail next to the road we decided to play with him by throwing checker pieces in the gaping hole that was its mouth. It was fun while it lasted, but eventually the snail got bored and left. Turns out it was sitting on a radio all this time! It's working, we just need to ... clean it up a bit."
- Mary Jane hates the Checkers, according to the event when the player gives her the Checkers on her birthday.