The side plates contain the lock mechanisms for the right and left barrels. The lever is attached to a long screw that seats in the right lock. Turning the lever counterclockwise removes the screw and allows the lock plates to be removed for inspection, repair etc.

The slotted screw in the fences secures the bushed striker - the cylinder in the breech face that houses the firing pin. It also acts as a gas relief valve if the firing pin pierces the primer.

Such a long, long time to be gone, and a short time to be there.