Trying to crack a Homebrew linear amp to learn how it works

This is something that is wrapping my brain as of late. My local ham radio club has a legal limit + Amplifier that was donated many years ago by an avid homebrewer. The main problem that I and the club face is that the homebrewer who donated this amp has been SK for quite some time and me and the president of the club are stumped trying to figure this thing out.

http://imgur.com/a/nR7WR