Olympus PME, MJ, N, MF, MG and POS microscope lamphouse assembly.  Also, from the literature, it appears to fit the Olympus LSP oblique illluminator. All of these microscopes are reflected light units from the mid-1970's and I know of no other applications for other Olympus microscopes.  The attachment point to the microscope intermediate tube is 24.5mm with a locking screw and the lamp socket opening is 29.5mm with a compression fitting with screw. The lamphouse has two screws to center the lamp filament. No socket or lamp are included, the lot consists of only the items pictured. The sale if for one each. Thanks for looking!