Unlikely you saw one at walmart. That is a 3-speed planetary gearbox. The system consists of one large sun gear, three sets of planets of varying size on a common carrier, and three separate ring gears. The input is the planet carrier, the output is the single sun gear, which creates an overdrive in each gear. To select a gear, one of three ring gears is stopped by the 2-cable selector switch, which uses a single dog to engage radial dogs on the outside of the ring gears.
Thanks for posting.