This assembly is built from 4 printed circuit boards. Three of the boards form a 5 in. by 6.5 in. sandwich which encloses the actual core arrays. The bottom board of the sandwich has a double sided edge connector which is located at the front of the assembly. The sandwich is attached to the top of a full size 4 layer board. This main board has a double sided edge connector at the back and the remaining area on its top is populated with DIP integrated circuits and various discrete components. The left card extractor has "SSA" stamped on it.