Nice! But still can't se anything that tells me that it is a LSD..
And where is the other sidegear?
Maybe the Volvo LSD is limited on one gear? Not both like the one described in the webpage I wrote before..
Have never opened a Volvo 300 diferential 
http://www.janiervast.com/kuvat/lsd/differential.jpgLook part number 7, that is reqular open differential gears and gear case, now this part that I have replaces that stock part.
These gears in this LSD unti don't move with hand powers, but that stock part that is open differential, there I can easily rotate gears.
I think that lsd clutch and plates are inside of that black lid that you can see in those lsd pictures, there is around 3cm space for them.
As you can see from above link that other sidegear is in that big gear plate side, it attachs to hub, that has bores, with bolt (245nm power needed for it) that goes trough hub, and that hub attachs to driveshaft with 6 10mm bolts.
Could be that it is not very strong part, but other driveline parts in 300-series are not too strong either, when comparing to 200-serie

Bit hard to explane as I have never opened any differential and also english is not my best language

Edit:some mistakes removed
Edit2: Oh yes, this LSD unit that I have contains parts 2 and 7 from that picture
Please feel free to ask more if you have questions, I try to answer as well as I can.