The Topo II (Digital Topo) quickly changed the colors of the stickers to black and then added a signature plate from Nolan Bushnell. The quickest way to tell if it is a Topo II is the button on the head is red, but still has the folding arms. The Topo III does not have folding arms, but has the same red button on top of the head. The internal electronics are the same on the Topo II and Topo III. They both use the IR transmitter, where the Topo I or Analog Topo used a radio transmitter.