A couple of the earliest electronic calculators and the beginning of Casio Computer, the 14-A (1957) and AL-1 Programmable (1962). Both use hundreds of mechanical relays as logic units and cool old-school displays. (Sorry the vid is Japanese only, but you can still see/hear everything.)
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I remember in the early 1970s they started introducing solid state pocket calculators, they could add, subtract, multiply and divide and cost ~$400. By 1975 I got an advanced one that did roots, exponentials and even solved polynomials for about $100.