This is a Spex model 1870B spectrometer for parts only. It is missing the grating, but more importantly, it is also missing the deflection mirror assembly for the ‘input’ slit. It features a focal length of 0.5 meters and fully adjustable input and output slits. The input slit is a type 1451N and includes an additional slider to adjust the slit height in steps. The output slit is a type 1451X mounted on a type 1871 adapter plate. Both collimation mirrors are present and in superb condition (no haze, scratches, or marks). Both slits function properly. Overall condition of the instrument is very good. Serial number is 3651.