It's just an extension of the tachymeter onto the second rotation of the chronograph second hand. There must have been something significant about 50, because that's a feature of all the later Eberhard chronographs. Perhaps 50kph was a speed limit?
50 km/h is the urban speed limit in Italy, the Eberhard's natural environment, but who puts a speed limit on a chronograph? That can't be a selling point, especially in Italy, except maybe to the carabinieri. 50 km/h is for horses and bicycles. I think it was just an excuse to put a little red pop on the dial. Some of those contodats have red date wheels, and it would have made a nice balance.
Well the FOIS didn't arrive but a bracelet that I wanted to try on my 2913 did. not a total loss, will see the FOIS on Tuesday morning. I thought you were supposed to get more patient as you got older馃槨