Independent 0510 Instruction Manual page 57

Tachymeter
(common feature for Cal. 0510 and 0520)
To determine the average speed, start the chronograph simultaneously with the
start of measurement.
Stop the chronograph at the point 1 kilometer away from the staring point. An
approximation of the average speed over that distance can be determined by the
position of the second hand at that time.
For example, if it takes 45 seconds to travel 1 kilometer, then the average speed
over that distance is 80 kilometers/hour.
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