Nikon Rotating Slide Plate Holder for Nikon Inverted TMD diaphot. This unit is new in original packing only opened to photograph. It is probably after market from A.G Heinze with a product number H224ROT and a last list price of $780.00 It is intended to be used on the diaphot TMD inverted microscope and maybe others. It measures 160mm X 110mm. The insert hole measures about 95mm and has a spring detente lock. The rotation is smooth as silk and only unwrapped to photograph.  Included are the attachment screws and corresponding Allan screws. Thanks for Looking!