HP 25C HewletPackard Scientific Calculator 

"The HP25C was introduced with the HP67A and the HP97A on the first of July 1976...Apart from one significant difference it was exactly the same as its predecessor, the HP25A. Even its codename "Squish" and its $200 price were similar to the codename "Squash" and the $195 price of the HP25A...If the codename Squash suggested that a lot of features had been squashed into such a small package then the name Squish correctly implied that yet another feature had been squeezed in. This feature  the significant difference  was that the HP25C was the first calculator with "Continuous Memory", as denoted by the letter C after its model number." Wlodek MierJedrzejowicz.  
Source: MoHPC  The Museum of HP Calculators 
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