1. stick head under car
2. put hand on top side of diff if ur so unflexible to lean up and swivle ur head a bit
3. find bolt, move hand clockwise to next bolt, repeat until ur hand is in the same position it started in
4. add up total number of bolts
better yet, just looking at the first pic i can tell it's a T18 diff with sway bar mounts - which means its off a later model T18.
If it has discs, there is quite a possibility that this is a jap differential, but also could be a T18 diff with discs adapted.
The way i would tell is the end flanges - if you 'stick your head' behind one wheel, and look at the flanges which adapt to the backing plates of the brakes, it should either look like these: