Some of the earliest seals were the cylinder seals of the Near East. Cylinder seals, made of stone and other materials, were rolled over clay to transfer a design onto the soft surface. The cylinder seal shown above is in the collection of the Musee du Louvre, Paris. For more information, see:
www.bu.edu/anep/LB.html
http://www.lacma.org/programs/ArtWorkMonthcylinderseal.aspx
http://home.nycap.rr.com/foxmob/cyl_seals.htm
On ancient seals from the Indus Valley see:
http://www.csuchico.edu/~cheinz/syllabi/asst001/fall97/2chd.htm
http://www.metmuseum.org/toah/ho/02/ssa/ho_49.40.1.htm