Nowadays we sign our documents and letters, and stamp certain documents with official seals, in order to assure their authenticity and to convey personal or official authorization. For the same purposes, people in ancient Mesopotamia sealed their clay documents, using small stone stamps or cylinder seals.
A seal was typically carved with a pictorial scene and an inscription naming the owner of the seal. When pressed or rolled onto a clay tablet, the seal left its distinctive impression in reverse on the clay. Like a signature, the seal impression uniquely identified the seal owner, and conveyed his or her authorization of what was recorded on the tablet.
Here are some examples of sealed clay tablets:
This tablet on the left records three acres to be harvested by Dada, the swineherd. The official in charge, Lugal-emahe, rolled his seal all over the tablet. Dada was to harvest a three-acre plot, planted in barley, located in a place called “Field of the Ash Trees.” Assuming that ash trees did grow at that place, maybe their branches were used to make Sumerian bats and hockey sticks!
This tablet on the right is a receipt for beer, sealed by a clerk named Umani.
On both tablets, the seal was impressed most clearly in a blank space left for it on the reverse, between the month and year of the date formula.
The tablet below records numbers of laborers assigned to certain tasks, and it was sealed by the overseer, Akalla.
See the total on the left edge? It reads: “201; 7 sick.” In the sexagesimal number system used in cuneiform writing, a vertical stroke or 60 stands for 1 or 60, its value depending on its place (just like our place-value notation), and an angle stroke stands for 10. So = 201.
The text on the right tablet reads:
86 laborers, for one day, levy ...; 107 laborers, for one day, stationed at the Amar-Suen-egar canal;
7 sick laborers;
8 laborers, for one day, stationed on the water; Foreman: Lú-sig.
Seal of Akalla, the overseer.
Year Enunugal was installed (as priest of) Inanna.