The very first unit for sale I believe is for 1st generation Blazer/Jimmy trucks. I'm pretty sure I bought that exact unit from JC Whitney and put it on my Blazer. In the picture the inner threaded brackets are not shown so I don't know if it was complete. In the eBay add one you can see the two inner threaded brackets. They go inside the fender and the one with the 1/4" round rod on it is the upper bracket. The rod was to help you put it up in the very top corner of the rear so you could put the bolts in. Once it was in you could twist the rod off the bracket to remove it.
Looking at the top one again, even though the brackets look the same as what I had, the main bracket is even and not tapered like the second and last one pictured. It is too narrow at the hinge end to mount on a blazer rear body and is either a Scout or Jeep unit.