What is a United Nations document symbol?

The symbol is usually found at the top right corner of a document. A symbol serves as a unique identifier for a United Nations document. Each symbol is composed of numbers and letters which do not give any significant indication of the subject of a document. All language versions of a document carry the same symbol. Some publications have both a symbol and a sales number. The publication "United Nations document series symbols, 1946-1996" provides more information about the symbols used in this period. (ST/LIB/SER.B/5/Rev.5).