Hexadecimal mechanical calculator from the 1970s
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1840s "Universal Calculator" Review / HowTo Lalanne's Abaque
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Multiple-tally Denominator Review / HowTo
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1950 Curta Calculator
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The 3D-Printed Curta Calculator
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Some silly number systems
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1840s calculator! Palmer's Pocket Scale Review / HowTo
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Magic Brain: Last Gasp of the Mechanical Calculator
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