Long box with a hole, a ball to drop in and a drawer
This toy is a version of the object permanence box that is a bit more advanced (introduce it after the object permanence box). Here your baby will practice using their both hands as they can hold the box with one hand and pull the drawer to find the ball with the other. When they open the drawer, they will see and learn that the ball still exists even if they didn't see it before.
Introduce this toy when your baby is approximately 10 months old.