Extract from The PC Pioneers
Steve Wozniak was solely responsible for the functional design of the Apple II computer.
Steve Jobs wanted the look and feel of the Apple II to be different, to be more like a home appliance, to be a complete ready-to-use computer and not a hobbyist product.
The case was defined by designer, Jerry Manock who was hired by Jobs just nine weeks before the product’s launch at the West Coast Computer Faire.
The case was to have a sleek look, more like a calculator or typewriter. It had no obvious fixing, all the screws came from the underside, and the top could simply be lifted to insert additional cards; usually the monitor sat on top of that flap. The case was made in polyurethane using a reaction-injection moulding process. The quick and inexpensive approach proved however to be somewhat irregular and a number of the Apple II cases required hand finishing by sanding the joints.
The paint used was also inconsistent in terms of its adherence to the case. Later production moved over to an acrylo-nitrile-butadiene-styrene plastic which did not need finishing or painting; it proved to be both smoother and harder wearing.
An Atari engineer, Rod Holt, was approached to develop the power supply as analogue circuitry was not one of Wozniak’s skill sets. The heat from the power supply needed to be dissipated, so this and the expansion card slots determined the height of the case.
But the rest was all Wozniak.