"War of the Robots" (1966)

The new dome has an unusual new feature. A single keyhole-shaped gasket has been added behind the ear piece and cooling rings. This new, larger gasket has taken the place of the old rectangular gasket that previously adhered to the dome beneath the cooling rings.

Experts speculate that this larger, more comprehensive gasket was added because the hole in the plastic dome through which the ear protrudes was carelessly cut. It may merely be a patch to disguise poor workmanship, but it nevertheless enhances the appearance of Robby by adding an interesting visual detail that unifies those elements that protrude through the dome.