This is an International Light IL782A research photometer head (serial 317) with a PM271D photomultiplier detector (serial 1197) and an SIW #337 input optic. The IL782A section has a micrometer adjustment and a filter slide. The PM271D uses an S-20 photocathode covering 200 to 850 nm with a 420 nm peak and a range of 3 x 10^-14 to 3 x 10^-7 W/cm², so it suits very low-light work such as bioluminescence and phosphorescence. It requires a regulated high-voltage supply such as the IL760D and a compatible International Light readout such as the IL1700, which is not included. The lot includes the head assembly, a white-faced round disc, a cable with a multi-pin connector, the power supply instruction manual, and the fitted hard case. It is ex-university lab equipment with handling labels on the housing.