I knew I'd seen it somewhere...
Milton, it is in the C-60 0003635_erection and maintenance instructions (.pdf) on page 189.
(a) The door for entering the airplane is quickly removable in flight and equipped with a lock which can be secured and opened from the outside. A lever releases the hinges. A removable cover plate replaces cabin door during parachute troop maneuvers.
Further along it says:
(5) EMERGENCY EQUIPMENT.
(a) Two emergency panels, (note: the window hatches) operated from the inside, are provided. The entrance door is quickly removable for egress in an emergency. A lever releases the hinges of the door in flight.(note: for use in emergency bailout) Also an easily removable cover plate for the door opening, removable from the inside, is supplied...