optocoupler ID

[UnionTech]

Hi guys this is my first post and hoping someone can help me out with a part ID. This optocoupler came off a PLC-2 allen bradley digital input board. My guess is its a darlington pair but wanted to see data sheet to know specs. I have had no luck searching Q4788 which i think is part number. When I tested with an ohm meter i have 450k from base to collector and 900k base to emitter. I think pin 6 is base 5 collector 4 emitter 3 unused 2 cathode 1 anode. I attempted to attach a decent photo of the part. Thanks in advance

 

[UnionTech]

How about the theory that the optoisolator has a darlington pair output? I'm pretty new to electronic repair and basically doing it as a hobby so not sure why they would use that paticular optocoupler for this application. Or any tips on how to ID it with a meter and test circuit?

 

[shrtrnd]

When I worked industrial electronics, I often had to find whatever office in your company
had the 'as built' literature from the contractor. Somebody, somewhere, has all the
literature and schematics for all of the equipment installed during the job.
I'd be looking for a schematic with the part numbers on it.

 

[GonzoEngineer]

Looks like an opto from General Insruments.