HP 25 HewletPackard Scientific Calculator 

"Introduced on August 1 1975, six months after the HP21, this was the eighth equal (with the HP22) handheld electronic calculator sold by HP, and the first really powerful yet small technical model  the same size as the HP21 but with more functions, and programmable to boot... Its codename, "Squash", might be an allusion to the amount of functionality squashed into such a small package" Wlodek MierJedrzejowicz.  
Source: MoHPC  The Museum of HP Calculators 
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