Individuals and administrative bodies used seals to denote ownership of items and to authenticate documents. A man typically carried his seal on his robe for easy access. Wearing a seal became recognized as a method of protection and good fortune. The earliest stamp seals have dated to ~6000 BC, excavated at Neolithic sites including Catal Hoyuk and Hacilar. Neolithic stamp seals were flat with geometric and abstract shapes. Animal forms appeared on stamp seals by the start of the Early Bronze Age (~3500-3100 BC). Simultaneously, cylinder seals began to appear ~3500 BC. Cylinder seals were better than stamp seals for impressing onto clay tablets and pottery jar caps. These were great for overseers, as they could be used to avoid skimming from the top.
The cylinder seal was a small cylinder, usually no more than 3 cm high and 2 cm in diameter, of hell, bone, faience, or a variety of stones (eg, carnelian, lapis lazuli, crystal) in which a scene was carved in a mirror image. When rolled over a soft material -- usually clay bullae, tablets or clay lumps attached to boxes, jars or door-strings -- the scene would appear an indefinite number of times in relief, easily legible. Technological knowledge required to create cylinder seals was far superior to that required for stamp seals, which had appeared in the early Neolithic period. From the first appearance of cylinder seals, the carved scenes would be highly elaborate and refined, indicative of the work of specialist stonecutters.