Mines empty too. Manual says its an auxiliary box, has some straps in there too. Manual shows those straps as being able to hold down things inside so they dont move/rattle.
Mine had the first aid kit in there, but I have no idea if that's where Toyota put it or where the PO put it. I currently have a trailer hitch strapped down in there and some ratchet straps stuffed around it, with the first aid kit now handily velcro'd to the back of the rear seats. Loving the storage in this thing compared to the R50 Nissan I had before.
Mine was empty when I got my 4R so I use it for ratchet straps, a machete for hiking trails, an extra quart of oil, a rag for checking fluid levels, gloves, and TP. [emoji1303] also a can of Tri-flow lubricant.
I have it on my driver side of my GX. Perfectly fits a VIAIR portable fuses etc and I put a molle panel on the outside for additional storage. Trying to find a molle bag big enough for my jumper cables.
When I purchased my 2008 model year V8 SR5 new in Feb ‘09, that right hand compartment contained a Toyota-branded drop hitch minus any ball and a packaged Toy-branded wire harness for connecting a brake controller. The leftmost strap is perfectly located against that molded step to hold the drop hitch w/ball.
These days I keep similar stuff as mentioned above: the Toy-branded drop hitch plus ball, utility towels, small mechanic’s tool set and various other towing needs in there.