Jog Wheel Brightness

@S-TYPE > That can happen if they're from two different production batches and the part supplier changed or spec of the component changed between them. It happens all the time with hardware production. While I understand it's an issue of aesthetics, the good news is it's only cosmetic. You could have those changed if you know anyone decent with electronics, but Pioneer doesn't support or endorse disassembly, modification or repair of Pioneer DJ hardware.

How can I identify the batch number so I can try to find a matching pair?

Really, it would likely be a matter of checking the manufacture date, but you wouldn't be able to see that on the outside of a sealed box. :(

Pulse; The sticker that says the serial number and manufacturing date (MFD) is on the CDJ and the outside of the box.
If I could ask my dealer to see which other CDJs have the same MFD, I should be OK?
In my case, my March 2015 CDJ jog ring is brighter than my April 2015 CDJ.

There's no guarantee of this -- even two produced in the same month could be from different material batches. Sorry I can't really provide much more help on trying to determine this; the engineers would not release this kind of internal information.