That's the thing, there was no 'hatch' like you see for some of the drivers positions. The radio operator SOMETIMES had a periscope, but usually not. Those who had it really didn't use it, their job was to man the radio, using the machine gun was of secondary importance, and observing wasn't really done at all. Their entrance hatch was just a steel fliptop, it was only open when they would be sitting outside of their positions, something they simply wouldn't be doing in combat.