Originally a cipher consisting of a single letter, later a design or mark consisting of two or more letters intertwined. The letters thus interlaced may be either all the letters of a name or the initial letters of the given names and surname of a person for use on notepaper, seals, or elsewhere. Many early Greek and Roman coins bear the monograms of rulers or towns. Most famous is the sacred monogram, which is formed by the conjunction of the first two Greek letters of (Christ), usually with the (alpha) and (omega) of the Apocalypse on each side of it. The Middle Ages were extremely prolific in inventing ciphers for ecclesiastical, artistic, and commercial use. Related devices are the colophons used for identification by publishers and printers, the hallmarks of goldsmiths and silversmiths, and the logos adopted by corporations.