The Siemens 3RG7421-0AB35 is a SIMATIC PXO320 K21R retro reflective photoelectric sensor with a built-in polarisation filter. It runs on DC 10-30 V and switches PNP light-on at up to 150 mA. The sensing range is 3 m, and it comes with a 350 mm PVC cable terminated in a Molex connector. The package is 31x20x12 mm with M18 optics, sealed to IP68.
The polarisation filter is the key feature here – it lets the sensor see through shiny or reflective targets without false triggering. That 3 m range is the rated detection distance with the reflector; out here in the grease, you'll get a bit less if the lens gets a film of oil, but IP68 keeps the washdowns from killing it. The M18 optics thread into standard mounting brackets, and the Molex connector means you can swap it fast without rewiring a whole gland plate.