Now this is a totally classic advertisement! The dishwashers featured in the ad are the first generation of Kitchenaids Hobart made. They had a horizontally mounted pump with a clamshell pump inlet in the sump that moved the water right up into the discharge/washarm support.
Note the filters as well.. the round one would be lifted up by the drain solenoid to let the water drain out by gravity.

These were clones of the original Hobart UM-1 series which were followed by the vertical pump designs we are more familiar with.
That design allowed the use of a drain pump coupled to the bottom of the pump motor to drain the machine and not have to worry about a gravity drain. Amazingly, it was NEVER an option of the commercial models. The first true drain pump machines which did not employ the overflow tube was the Hobart LX series machines. Even the WM series which was based on the 16 series Kitchenaids had a pumped drain but had the overflow tube in the tank so the pump could not pump higher than the overflow.In reality, it was a pumped gravity drain.

Incidentally, one of my Aunts actually had one of the machines pictured in the ad. Worked damned good too! I think she bought it out of a Buy-Lines ad for like 20 bucks back in '67.I bet if she had kept it, it would still be running!

Great ad and thanks for the info!

Funny how the ad pictures a wash-arm that bears no resemblance to the actual water-spray pattern.

I'm kicking myself because I let an old KitchenAid Imperial KDI-12 go by last year with that beautiful spray arm. Beautiful ad, I agree and thanks for posting it. I love those old KitchenAids with the cycle dial on the lower panel. When anyone asks me what dishwasher(new) to buy I always tell them to go find a vintage KitchenAid, 2nd, a vintage Maytag Jet Clean and lastly (and most difficultly) a GE pull-out.