Leitz 40X EF Microscope Objective number 519762.  It will fit the Leitz Laborlux series of  160mm TL microscopes.  The numerical aperture is (n.a.) 0.65 and it requires a coverslip thickness of 0.17mm.  This objective works very well with other microscope makers from Nikon, Olympus and Zeiss as long as they are a 160mm TL version.  All glass is free from fungus, dust, scratches, element separation, or oil fouling of internal lenses. The image is very pristine, just like new.  THE SALE IS FOR ONE EACH