OK, it doesn't have volume and tone controls because it is just a power amp, there is no preamp there. That is also why it is not very loud. You'd need a peramp for any tone and volume controls as well as overdrive of any kind. There are no gain stages.
Is that coke bottle tube a 2050? If so it is a tube version of a triac, and would have been used to turn the leslie motor on and off.
The amp survived all these years without a standby switch, I don't know why it needs one now.
What are the four output tubes? 7868 maybe?
I can't make it out in the picture, what went in the empty socket?