I looked up all the numbers on the board on Google and didn't get any matches. I'm trying to find the pinout, it has 6 pins two on top 4 on the bottom. I'm thinking the two pins are for the IR emitter but I don't know how to wire up the other 4 pins. The unit is part of a DC motor assembly and I think it's an encoder but have no idea what's it called.
Was there supposed to be a picture or something?
Yup but first attempt said the was to big so I cropped it and made it smaller it think it worked this time.
The OP's image.
Can you get it from another angle? It almost looks like a beam break sensor but it's hard to tell.
Here is a couple of different angles of the full unit. There is a clear disk with graduated black line on the circumference of the disk. This setup is cheaper to use than use a stepper motor. But I can't find the reading unit anywhere. I can find units with wider slots something like .250 inch wide the one I have has a slot of .070 inch wide. I don't know if this will help you or not. But thank you for your response.
Yeah, it's a rotation sensor. The disk has slots or reflective lines. The device senses them, and so can be used to determine how much turning has happened.
Hi,
Can you tell us what machine it was on?
Possibly a printer or photocopier?
Tom.. 
I think the usual technical jargon for those things is "slotted optical switch"
There is an LED on one side and a photo diode on the other side. The connection diagram for this Sparkfun reflective sensor should work with your device also. I use what Sparkfun call an analog circuit to detect digital pulses using an interrupt.
I have salvaged a few of those slotted switches from old printers etc and they all seem to work with the same circuit.
...R