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hp 25 00hp 25 01Model: HP-25
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Year: 1975/1978
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Info: The HP-25 was a hand-held programmable scientific/engineering calculator made by Hewlett-Packard between early January 1975 and 1978. The HP-25 was introduced as a cheaper (US$195 MSRP) alternative to the ground-breaking HP-65.

 

WIkepedia HP-25


 

hp 35 01hp 35 00Model: HP-35
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Year: 1972
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Info: The HP-35 was Hewlett-Packard's first pocket calculator and the world's first scientific pocket calculator: a calculator with trigonometric and exponential functions. It was introduced in 1972

WIkepedia HP-35


 

hp 35 01hp 35 00Model: HP-38 E
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Year: 1978
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Info: The HP-38C and HP-38E were the high-end business members of the 30 series. The HP-38E was introduced first, followed a year later by the HP-38C which added continuous memory.

HP museum HP-38 E


 

HP 41 c 02HP 41 c 00Model: HP-41C
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Year: 1979
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Info: The HP-41C series are programmable, expandable, continuous memory handheld RPN calculators made by Hewlett-Packard from 1979 to 1990. The original model, HP-41C, was the first of its kind to offer alphanumeric display capabilities. Later came the HP-41CV and HP-41CX, offering more memory and functionality

WIkepedia HP-41C


 

hp 45Model: HP-45
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Year: 1973
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Info: The HP-45 is the second scientific pocket calculator introduced by Hewlett-Packard, adding to the features of the HP-35. It was introduced in 1973 with an MSRP of US$395 (equivalent to $2,411 in 2021). Especially noteworthy was its pioneering addition of a shift key that gave other keys alternate functions.

 WIkepedia HP-45