And thanks to a nice family of fellow watch collectors and friends who sold me the CQ-1, I have received - as a gift (thanks again!) - also the Casio CQ-1's younger (step)brother

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CASIO ST-1 + original Casio leatherette case (cca 1977) -
World's first digital stopwatch + calculator with Time computing (TM), as one can see in the photos below,
including an old advertising of its quite advanced functions for 1976-1977, functions who made it the ideal device for engineering related TIME and MOTION studies and also for AUTO racing :
One may also read an interesting story, about how these devices may have been used in Industrial Engineering - Time Studies - even in early 80's - below:
http://goodmorningyesterday.blogspot.co ... uiz-1.htmlThe original Casio ST-1 package (without the manual):

and a nice advertising of CASIO ST-1, showing some of its advanced functions:

Regards,