Tapped hole visible behind sensor is M2. Looks like 5 wires that go to the outside of the sensor.
Button head screws in the second picture are M3 for scale
Sensors are held in from the front with one M2X5 button head cap screw
Needed to support some older equipment. the only part numbers found for this don’t yield any results when searched: 151517 GCE Optical Sensor
Please help! Thank you very much!