In 1949, according to the June 15th, 1949 issue of Electrical Merchandising, when APEX bought all of the capital stock of Lake State Products, Inc. of Jackson Michigan, producers of what would be called the Dish-A-Matic, the Apex Electrical Manufacturing Co. was located in Cleveland, OH so I guess they stayed there. According to another article, 1957 was the last year of APEX production. Various design elements might have been used by WCI under other labels as I think we have seen in other PODs of department store catalogs whee the machines had APEX features.
The double wall Fiberglass tub was advertised as insulating the wash water so that it did not cool. If you notice the little holes that feed into it, as opposed to the larger holes that threw water into the drain tub, it also filled during the spin drain to help stabilize the tub during the initial phase of the spin. As the tub speed increased, that water was thrown back out. I think that was the way it worked. The Fiberglass did not have the strength of a steel tub so having the water jacket might have helped prevent stress on the tub in the early stages of spin when tubs swing off balance a bit, maybe. Apex was big into Fiberglass. They used it for the lid on their portable dishwasher.