Well, they're big and heavy. :wink:
I had one apart and came to the conclusion that the block diagram printed on the bottom (which is your third picture) bears only scant resemblance to the actual circuit design. My chief reason for thinking so is that the output impedance changes a good deal when you change the gain, which suggests a variable-feedback output rather than the straight pot and fixed output stage they seem to be suggesting in the diagram.
Oh, and the specs for gain range are way different than what it actually does.
Peace,
Paul