Here is a very nice spring loaded Leitz 100X NPL Fluotar oil immersion microscope objective with internal diaphragm. It is intended to be used on 160mm TL Leitz microscopes but could successfully be used on other manufacturers such as Nikon, Olympus, and Zeiss. The optical and cosmetic condition are excellent with a huge  n.a. of 1.32!  It requires the use of a cover slip with a thickness of 0.17mm. For darkfield observations this lens excells with the use of the internal diaphragm. The lens is free of dust, scratches, fungus, oil incursion into interior elements or element separations and the diaphragm works as intended. The objective was mounted on a Nikon Microphot 160mm microscope for evaluation and found to be in excellent condition while examining a stained tissue slide- image was sharp, contrasty and fully color saturated. Thank you for looking, you will not be disappointed with your purchase!