This was a main lug panel, both the ungrounded conductors are taped off in the first picture. The Main, in with the metering about 60' away, was also an FPE.
Scott, I'd have to say scenario "C"
I don't think this panel was opened since it was installed originally.

Here's the parts as they laid out. You can see the 8-32 screws that you mention, mxslick.

[Linked Image]

Kind of like a sick jigsaw puzzle.