The same size as our owl turn, this is used on the hall side of the door for access to unlock the door in case of an emergency.  The round opening is accessible to an emergency release key or a screwdriver.
 
A brass owl emergency release is a decorative and functional component often used in vintage or antique door locks. It is designed to release a door latch or lock in case of an emergency, providing a quick and easy way to exit a room or building.