Unlike today, Heuer used to specialize in far more than watches - to include stopwatches for sports timing, yachting, science and research (like the example here), automotive, aircraft, and far more.  
 
Its stopwatches - like the 1969 Heuer Ref. 403.406 scientific research stopwatch here - were designed to measure everything from 1/5th a second to 1/100th of a second, and the example here measures 1/10 a second (with a 10 minute subdial) and was designed for science research and sports applications.  Sports events included rodeo, track, swimming, and general "allsports time athletics"
 
Per Heuer literature of the era, the 1/10th second stopwatches were most frequently used for measurements in laboratories, research, and sport.  Per the Heuer catalog, these stopwatches were "generally used when particular accuracy is required and the measured time lies under 10-15 minutes.  This is especially true for all short- and middle-distance track events (under 1500m), swimming and precise scientific measurements.  The minute register models offer greater legibility of the 1/10 second, but have shorter register capacity than the 15 or 30 minute models."
 
Operations are via a central crown, with start, stop, and return to zero by successive depressions of the crown, lending to simple time measurements, for example the duration of chemical reactions, track timing, etc.