Nope. There were no controls at all on the 'slave' amps, just an input jack from the master. (I never saw one, just pics and that was ~50 years ago). Without the master it was just a big, heavy box-with a striped grill. The amp was inside the cab. Couldn't be seen unless you removed about 20 +/- screws.
As long as the electrical circuit could handle them, there was no limit-other than space-to how many could be strung together, i.e., you could have M+1S* on one side of the stage and another 2 S's* on the other side, all controlled by the 1M. Would made a helluva racket.

*or 2, 3, 4, etc.