Nikon auxiliary objective lens 0.4X to fit the "Old Style" Nikon stereo microscope SMZ-2,  SMZ-5, and SMZ-6. The SMZ-2 and SMZ-6 have a zoom ring as opposed to two black zoom knobs. The SMZ-5 is a fixed 2.0 magnification microscope.  The lens is in excellent optical condition without scratches, fungus, dust or delamination.