The Festo SIEF-M12NB-PS-S-L is an inductive proximity switch from the SIEF series, classified under Inductive Sensors / Proximity Detection Switches. It is a current-production part, so it remains a standard BOM line for new builds and spares.
M12 shielded inductive sensor with PNP normally-open output. Detects ferrous targets at standard sensing distance for flush mounting.