Hey there Guys, can anyone tell me what KJ 0518B stands for. It is stamped in the rear axle passenger side front.It has a 12bolt cover as well.

Additional #'s
3917124
CON1
GM52
E88

Thanks

I find it as a 3:55 non-posi.......May,18 from the Buffalo plant, this code KJ was used throughout the late 60's