Serial number of a 3.23 differential?

[SnakeDoctor]

I'm going to be picking up a 3.23 differential from an M3 locally in a few days and I want to check the serial number just to be sure. Could anyone tell me what it should start with so that I'm sure I'm getting what I pay for?

[MikeE36]

If you tell me where to find the number I'll go check mine. I just crawled under it but didn't see any real apparent numbers. I'm assuming its even on the diff...