Majestic/Grigsby-Grunow Volume Control

[resnatron]

A friend asked me to take a look at a Majestic (Grigsby-Grunow) Model 60 for him. It is a nice, big floorstander on legs with a huge (read: HEAVY) clamshell chassis. I brought it up slowly on a Variac but got no sound at all. Replaced 13 caps (non-electrolytic) and now it plays pretty well.

Now for my question, there seems to be no volume control? There is a tuning shaft hooked to the capacitor (obviously) and another 3-step switch for "Audio something or another" That's it for user controls. On the schematic from Nostalgia Air there is a Volume Control indicated on the bottom of the inner part of the chassis, but no way to control it, that I can see. There is a mention in the schematic about "automatic volume control" but I can't see how it works.

Any insight? Are there old radios with no volume control? Any help would be greatly appreciated.

Thanks in advance.

Paul