Modular electronics used in late 50s/very early 60s before Integrated Circuits were created/produced. Largely for military usage, where environmentant stability requirements were much higher and conventional components had alot of trouble. The components could also be packed more densely than discrete components (the picture shows a stack of about 10 components into that small volume - all already interconnected within the package).
Miniature PC boards were wired together on their edges and each board had at most only one or two compoments (resistors/capacitors/transistors/inductors) to build up comonly repeated ciruitry and put into a hemetically sealed case. The components could be mass produced and tested versus alot of electronics which were still largely hand-assembled at that time.
Lookup "Project Tinkertoy" on the Web
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