Rock a Stack

Rock-a-Stack is a toy by Fisher-Price with colorful rings that have to be placed in order of size onto a pole. It is designed to teach young children about colors and to help them develop their eye and hand coordination. Since the introduction of Rock-A-Stacks in 1960, over 40 million have been sold. Ernest Thornell was the designer of this toy (from a phone conversation on 8-31-16 between Ernest Thornell and Eric Smith).