The Standard Abacus of Isaac Ozen is a 3223 years old piece made by Isaac Ozen, a merchant living in Istanbul / Constantinople / Byzantium.
Considering its age and the quality of the work, people consider it of high value.
It is engraved with central asian patterns and some symbols pertaining to Ancient Mesopotamian religion.
This piece doesn't exist, but as a legend. It is said that in the year -1215, Isaac Ozen, the owner, made use of it in Istanbul / Constantinople / Byzantium to empower the Ozen family. Now it is lost, or broken, we will never know.