File:Vintage Hewlett-Packard Model HP-45 Advanced Scientific Pocket Calculator, HP's Third Handheld Electronic Calculator, Introduced in 1973 and Discontinued in 1976 (38772251491).jpg - Wikimedia Commons
HP-46
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HP-35 - Wikipedia
HP-35
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Hewlett-Packard HP-41X Handheld Electronic Calculator, Engineering Model | Smithsonian Institution
Vintage Hewlett-Packard Model 21 Electronic Pocket Calculator, Made in the U.S.A., A Scaled-Down HP 25, Circa 1975 | Calculator, Old calculator, Pocket calculators
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HP Calculators
The Hewlett Packard Calculator Page
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SwissMicros Model DM42 RPN Calculator
Hewlett Packard HP 15C Handheld Programmable Electronic Scientific Calculator | eBay
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HP calculators - Wikipedia
Hewlett-Packard Model 35 Calculator with case - Science History Institute Digital Collections
File:Vintage Hewlett-Packard Model HP-16C Progammable RPN Calculator, HP's First and Only Programmable Calculator, Circa 1988 (9330369298).jpg - Wikimedia Commons
HP Scientific Calculator Model 10S – Electronix Express
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The Hewlett Packard Calculator Page
