This is the small abacus of <a href="//commons.wikimedia.org/w/index.php?title=Muhammad_ibn_M%C5%ABs%C4%81_al-Khw%C4%81rizm%C4%AB&amp;action=edit&amp;redlink=1" class="new" title="Muhammad ibn Mūsā al-Khwārizmī (page does not exist)">Al-Khwārizmī</a> abacus with base-five/ten. All upper beans have the five values, and all down beans has the ten values. Hypothetically, this kind of abacus was used on the paleography of modern numerals: five, six, seven (down beans) and eight, nine, ten (upper beans). It is assumed to have originated because <a href="//commons.wikimedia.org/wiki/Human" class="mw-redirect" title="Human">humans</a> have ten <a href="//commons.wikimedia.org/wiki/Finger" class="mw-redirect" title="Finger">fingers</a>.
<a href="//commons.wikimedia.org/w/index.php?title=Muhammad_ibn_M%C5%ABs%C4%81_al-Khw%C4%81rizm%C4%AB&amp;action=edit&amp;redlink=1" class="new" title="Muhammad ibn Mūsā al-Khwārizmī (page does not exist)">Al-Khwārizmī</a>
born around 780 and died around 850
<a class="external free" href="https://en.wikipedia.org/wiki/Muhammad_ibn_Musa_al-Khwarizmi">http://en.wikipedia.org/wiki/Muhammad_ibn_Musa_al-Khwarizmi</a>