The valve seat of the present invention is configured for attachment to the valve housing after the valve housing has been coated with a protective coating. The shafts are on opposite sides of and arranged symmetrically with respect to a center line of the shear. The other clamp member has a pair of prongs defining a slot for receiving the shaft of the locking device, the locking element being engageable with the prongs to lock the clamp members to one another at ends thereof opposite the hinge-forming ends. The determining unit determines whether image data is front-side data or back-side data at a time of duplex printing. The rotor is rotationally responsive to the application of a magnetic field at the MR fluid.