Various front panels from the 1620 stand in for the Colossus computer's front panels.
Year of feature (shown above):
It may also be of interest that in the first scene, when Forbin is touring the innards of Colossus for the final time, there's a shot where in the near background is what appears to be an authentic disc-drive from that era, with multiple discs stacked vertically.
CDC supplied a lot of the front panels of Colossus within the mountain installation. I believe this is mentioned in the credits.