Filter size 85mm.
Earlier versions have an all black metal barrel.
The smaller lever on the left stops down to check depth of field. The larger lever on the right locks the rotating tripod socket. Show is the 42mm Pentax screw mount adapter, attached over the Pentacon 6 mount. The lever near the rear of the lens opens up the diaphragm and sets the spring action. The activating plunger releases it, stopping the lens down to the pre-selected aperture.