Renovating a Supro 60 Lap Steel Guitar

Hi - here's probably my greatest challenge yet. It's a Supro 60 Lap Steel Guitar. The amp is built into the case.

Note the latest in power connection technology - simply plug it in to the nearest light socket.

Loudspeaker missing - the output transformer has a long lead to go to an external speaker , I presume.

Its history: http://www.vintageguitar.com/1884/supro-guitars-and-amplifiers-part-i-2/

Here's a youtube of it: https://www.youtube.com/watch?v=elLAbFvML0k

Some photos of a decent one: http://www.soundcheckvideos.com/vintage-guitars/supro_60_lapsteel_amp