This is a Nikon camera adapter for chip size around 2/3. The camera mount is ENG Bayonet type. Original Nikon product now surplus to requirements. The system is designed for use with Nikon Microscope T and F tubes.
Later model tubes may be used with adapters available from Nikon. The item "Nikon Microscope ENG Photo Camera Mount Adapter 0.6X for T2 TUBE" is in sale since Wednesday, January 20, 2021. This item is in the category "Business & Industrial\Healthcare, Lab & Dental\Medical/Lab Equipment Attachments & Accessories\Microscope Parts & Accessories\Microscope Camera & Lens Adapters". The seller is "ozmicro" and is located in Bundaberg, QLD. This item can be shipped worldwide.