Here's a Manatt-King Radio Company amplifier, with nothing else to go on I'm going to conclude this is a "KING" model and refer to it as such.
Half cage rear enclosure, I believe the selector dial at left is an output impedance selector to match up to whatever is plugged into those 4 pin Amphenol speaker output sockets, the loose trunk wiring of which we'll see in the upcoming gutshot.
It's hard to discern what's what here. Going left to right, I presume we're looking at a rectifier, pair of outputs, phase inverter and a trio of preamp tubes doing preamp and/or mixing duties. Come to think of it, I was just shuffling through a pile of amps without really digging into them, so chassis labeling may be evident underneath that carpet of dust.
More sign of post factory work. The series pair of CC resistors are clearly in a more modern package, and the PVC jacketed wire is also pretty suspect without a time machine. The tagboard circuit and over all layout is pretty clean though, so there's potential. What's this? I do say, we've had a cookout!
Wirewound B+ dropping resistor, a touch worse for wear..
..beyond which is an indicator this unit has had something of an electrical mishap in the past.
Smoke stains, never a comforting sign. When/if I get around to this one it'll entail spot checking everything down to the iron and more or less rebuilding it all. Pretty nice doorstop though.