This is a Thorlabs silicon photo detector in a housing that accepts the SM1 series stackable tubes. The active area is approximately 2mm in diameter. There is a recessed pot for adjusting the gain of the detector, but it is not calibrated.
The housing face is 32mm square and 25mm deep (less connectors and control elements). There is a 10-32 thread in the base of the housing for mounting purposes. The detector face is threaded to accept the 1.2 inch diameter SM1 elements. There is a cable with a round 5-pin DIN connector but the power supply will need to be sourced independently. The detectors appear to have been used very lightly, if at all.
Location MB 150
Photo set 1188