If you remove the axles shafts and everything bolted to it and take out the bolts circled,the Third member (or center chunk) etc will come out
This is probabley what the tag id's
The ring and pinion are in here.
Similar to 9in Ford,Toyota and isuzu as well as a bunch of other vehicles,it makes for swapping broken parts in remote areas alot easier than setting up new gears
The axle tube should have a BOM late would list date,vehicle etc on it.
Good news is onother gear set can be easily swapped w/o having to set up new gears