The people of ancient Mesopotamia had many baskets which had been sealed with a special mark pressed into a lump of clay. Government officials marked their property so nobody could steal it. Their neighbors further east in India and west in Greece, from the Early Bronze Age, about 2100 BC, learned to use seals too. By the Ch’in Dynasty, about 200 BC, people were also using seals in China.
You can also make seals and seal things. Seals can be made from anything hard enough to mark wet clay (or Play-Dough). You might try carving wood, or making seals out of clay and letting them dry. Be sure to design a seal which is different from anybody else’s!
Take a box, like a shoebox, and put something in it. Put the lid on. Stick a gob of clay over the join between the lid and the box, to stick the lid closed, and press your seal into it while the clay is still wet, then let it dry.
Or, just put a small object inside a gob of clay, then seal it and let it dry.
Now mix yours up with other people’s. Can you tell which belongs to whom, by comparing the seals? What if you were a thief? How would you try to steal this stuff? What problems would you have?
Near Eastern Seals, by Dominique Collon (1991). A good introduction for adults.
The Chinese Chop Pack, by Robin Tzannes (2003). About Chinese seals (called chops), and includes some real chops for you to use!