Greg, Thanks! One positive way of dating this as a 57 is to look at the shot down into the center of the tub. At first, these had a very coarse grill over the impeller. By 58, it was a plastisol-coated grid made up of maybe 1.25 inch squares. By 1959, that had been replaced with stainless steel "hardware cloth" with 1/2 inch squares which they stuck with until the intro of the wash arm models. The Power Shower came out in 59 and there was a built-in with it. It was the 24" 4 cycle roll out. John has one of the chain drive mechanisms for this machine. It ran like a garage door opener, but without a remote control.
We had two GE portables, the older one with the pink interior and then the very deluxe, all white exterior squared off machine with the blue Plastisol tub & lid with white racks. Friends bought it for their apartment and when they moved to the DC area, we sold ours and bought theirs since it was newer and had not had the use ours had. I don't know if it was the Power Shower or the reduction in water changes, but the new one did not wash quite as well as the old one, not that we took dirty dishes out of it, but there were certain things it did not clean as well. It was beautiful and had a very distinguised beige and white stripe pattern Texolite top with subtle gold flecks. The young family that bought our house in 1967 sure looked forward to having a dishwasher. Like all of the dishwashers of the period, the Utility and Utensil/Pots & Pans cycle was not a pot-smasher cycle, but a slightly shortened wash cycle with no dry to sort of prewash heavily soiled pans, supposedly during the meal, so that it would be ready to be unloaded when the dishes were cleared from the table and the pots could be finished by hand. We did not do things that way.