Hand Abacus (14 ore 39 min, 21 nov 2018 anni – 14 ore 49 min, 1 lugl 2019 anni)

Descrizione:

The Romans invented the hand abacus it contained several long and short grooves, and had up to five beads in each notch. The Romans developed their hand-abacus as a portable counting board-- the first portable calculating device for both engineers and businessmen.

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