8.75 diff - metal in oil (pictures). Is it ruined?

I thought 8 .75 diffs were strong, why is mine made of glass?

I've driven it fairly steady :-/ Dropped the oil only to do the 'right thing' and... balls.

When out, is there any tell tail sign to see what is 'at fault' ?
How would you tell if the SG is 'rubber ducked' ?

Thanks,