Mystery rear end

[Stainless]

Hey.... I found that clunky sound I posted about last week.... it was a U-Joint.... seems that there is some extra space on the rear yoke, so the joint just bangs back and forth in it.... The question is... what rear end is it? After an hour of wire brushing, I don't see any numbers stamped anywhere.... it is a 12-bolt, open rear end..... that's all I know.... buy why would the yoke be a different size than what seems to be fairly standard? It is about 1/16" or 3/32" bigger than the u-joint. Just enough to let the shaft slap around.... any thoughts?

~Sean