To remove this eye battery cover, place the camera on soft and stable surface, apply even and firm pressure around the metal cap, and unscrew it counter-clockwise.

The cover for the eye battery is the circular and ridged metal cap on the back-most part of the left fascia.

If it does not unscrew with your hand alone, you can use pliers and cloth to loosen it. Place a small cloth rag on top of the cap, grab the sides of the cap with the pliers, making sure to keep the cloth between the pliers and the camera to avoid tooling marks and any damage. Turn counter-clockwise until the cap loosens. Then unscrew by hand.