It was a crock the day some accountant "designed" it, and the only way from here is up. Jack up the doorhandles and put a new car in between.
The case seems okay, but a total internal transplant into a nice little 15W boo-teek amp with efficient 12-inch speaker would transform it into something worth owning and taking to a gig.
The only place for a restoration to original is safely in a locked glass case.
The "Lamington" isn't so much a design as a state of mind. What have you got/can get, how much imagination can you bring to scrounging the hardware?
The original, and a couple of variants;


http://www.ozvalveamps.org/ava100/ava100project.htm