EE-SX673A Slot Sensor make OMRON

A Google of optical slotted sensor should bring up some hits They Vishay, Omron or other manufacturer I see plenty as modules

In this video, we take a quick look at a Z axis intercept sensor on a SLA printer and then

slot machine pvz EE-SX674 from Omron Automation at RS

slot live rtp OMRON EE-SX672 NPN 5-24V Photoelectric T-slot Sensor Specifications: Sensors features: T Shaped; 5mm Slot; Differential Distance: mm; Supply Voltage