Where are the branch circuit grounds at this sub panel?
The conduit was often used as the ground in the older installations. . .
Now I do not want to open any worms up here…but since it appears to be paper in those raceways i will venture to say it is the old BX Cable. And I will only assume this as you know exactly what assuming does to anyone.
Lets just remember that BX Cable (GE Product ) was never tested for the outer jacket to be an effective fault current path…but I wont go to the dark side on this topic.
1984 construction, post BX?