Whose rear end is this?

[Stocker]

Now that I have your attention , this is in my '72, and no one's ever been able to tell me what it is. I've heard Eaton, GM Corporate, and Beats Me. All I know is I have either 4:10 or 4:11 gears, and it has never broken. Except for slight pitting on the third (pocket) pinion bearing, which gave it a slight growl on deceleration. And it's an open diff.

Anyhow, I am curious as to what it is, and whether any limited-slip units are available for it (True-Trac, whatever?). Thanks - I appreciate any info.