A vintage pocket chronograph, with highest speed at 120 kmph (74mph): a “Slow Chrono”
This pocket chronograph watch is able to read not only the current time, but also the technical development crossing the centuries. All thanks to its unique tachometric scale.
A premise about the tachometric scale: it allows to measure the speed of an object (such as a car) on a given distance, conventionally one kilometre. 10 seconds correspond to almost 400 kmph, and longer times reflect lower speeds (ie. 15 seconds correspond to 240kmph; 30 seconds to 120 kmph).
The tachometric scale of this pocket chronograph has a number of unique characteristics: it is painted on the enamel, the scale has the shape of a spring, it is coloured and… it starts at 6 o’clock! And this is because the speed indicated by the second hand before 6 o’clock would have been impossible for that age.
This is why the scale has to be spring shaped and coloured. During the first chronographic minute, the speed reading starts at 6 o’clock with the red numerals on the external minutery. During the second minute, it continues with the green numerals, before in the external minutery and after in the arch below the hour markers. It is possible also the third minute measurement, through the four black speed indications at the very centre of the dial: 27 kmph, 24 kmph, 22 kmph, kmph.
Very different speed standards from the current ones! But common as a reference point at that age: in Hausmann & Co. archives there are two more enamel dials with the same tachometric scale logics, even if with different graphic solutions.
This is why we call this watch the “Slow Chrono”!