Processor card. The CDC 7600 was the successor to the CDC6600.
It was again the most powerful computer of its time.
It still used discrete technology; other manufacturers were already using integrated circuits, but Seymour Cray didn't believe in using untested technologies.
The small 2mm square components are transistors, individually fitted to the board.
This card is from the London University Computing Centre machine.
As for their CDC 6600, part of the computer time on the CDC 7600 was allocated to large projects at other universities,