Answer: Abacus
Step-by-step explanation:
The longer slot with five beads below the Ө position allowed for the counting of 1/12 of a whole unit called an uncia (from which the English words inch and ounce are derived), making the abacus useful for Roman measures and Roman currency.
If you are wondering what they used as numbers that would be Roman Numerals being: I II III IV V VI VII VIII IX X