ExSp33db1,
Yes the DC-8 had the same hole and we used it for vacuming the cockpit in flight however, it was banned from use because some individuals sucked up nuts and bolts left by MX and they ended up stuffed in the vertical and horizontal stab.
It was also used to suck the cigarette smoke out of the cockpit. Another trick we used on the DC-6 was opening an over wing exit window and one cockpit window thus allowing for smoke removal and air conditioning while operating in the far south. This was needed desperately once as we had a severe chemical leak in the cargo which was causeing us in the cockpit to suffer breathing problems, watering eyes and vomiting. We did not have supplimental O2 at that time.