I had a call the other day. A friend had purchased an enlarger and MetroLux from another friend. The sensor in the enlarger, as it turns out, was an oldie. One of the first and probably the oldest one in service. Anyway, by the time the enlarger got to the new home, the MetroLux didn't work with it. To make a long story shorter, the sensor was wired the other polarity and the new owner had delete a sensor extension cable that had a reverse in it. Putting it together as was fixed it.
I tell you this because there might be another one or two of these out there. Morley Baer's old sensor is a candidate for this, but I don't know where that went.