1959 was the first RCA Whirlpool with the revolving spray arm principle that KitchenAid started for home use in 1949.Believe it or not, Whirlpool started making electric dishwashers around 1914,consisting of a round metal tub,a motor driven impeller, the racks,you'd load the machine, pour 1 gal. boiling water in the tub with a pinch of soap ,and washing soda,if needed,let run a few minutes manually drain into a bucket, repeat with clear water, lift lid, air dry.1935, dishwashers became automatic, starting with Hotpoint.In the 50s, only KitchenAid had a revolving wash arm,with 3 exceptions. In 1950, a private inventer with The American DW co.made a spray arm machine, and was fast gone.Around 1955, came the Waste King, which was the 1st with multiple cycles, having a floating power arm with 58 jets. In 1958, Hotpoint changed to the spray arm design, calling theirs Double Deck washing, consisting of a lower arm, a fixed tower with an oversized circular frisbee shaped head with spray jets. The 1959 RCA Whirlpool with filter stream washing, a single spray arm design, outcleaned ALL dishwashers ever made up until then, due to a great sprayer, a filter that gratly resembles today's euros , and an excellent cycle design. No puny 5 min. wash,two 1 min. rinses here. It had a pre-rinse, THEN the 1ST wash ,another rinse, a second 15.5 minute wash, two more rinses, dry. It was great, I had a portable version of it.