They were called producer switched because audio engineers would often have a knob on the mixing board that wasn't connected to anything. As enged1 said, sometimes a producer would want more highs or less compression or whatever. The audio engineer would let the producer tweak the knob, claiming that it controlled whatever parameter the producer was trying to change. More often than not, they would trick themselves into hearing a change.Kevin, your TC112 is a first-generation v1, 4-ohm cab. That means the top switch is the horn kill switch, and the bottom switch is the attenuator switch (top end switchable between 3.5 kHz and 17 kHz).
Duke doesn't make 'em like that anymore, so you have a potential collector's item - if you want to think of it that way.
MM
P.S. What are "producer switches"?
I'm not ashamed to say that I do it occasionally. Often someone will ask for some minor change, and even if I just pretend to change something without actually touching anything, they are usually satisfied. It's more of a "you don't know what you're really asking for" type of situation rather than laziness or trickery. The fact is that most musicians know roughly nothing about production, so it's often a game of soothing their minds while secretly soothing their ears (whether they know it or not).

