The S&P system was later standardized by the securities industry and modified as years passed. Stock symbols for preferred stock have not been standardized.
Formerly, a glance at a U.S. stock symbol and its appended codes would allow an investor to determine where a stock trades; however in July 2007, the SEC approved a rule change allowing companies moving from the New York Stock Exchange to the Nasdaq to retain their three letter symbols; The DirecTV Group was one of the first companies to make this move. When first implemented, the rule change did not apply to companies with one or two letter symbols, but subsequently any stock was able to move from the NYSE to the Nasdaq without changing its symbol. CA, Inc., which trades under the symbol CA, moved from the NYSE to the Nasdaq in April 2008 and kept its two-letter symbol.
Prior to the 1999 merger with Mobil Oil, Exxon used a phonetic spelling of the company "XON" as its ticker symbol. The symbol of the firm after the merger was "XOM". AT&T's ticker symbol is simply "T"; accordingly, the company is referred to simply as "Telephone" on Wall Street (the T symbol is so well-known that when the company was purchased by SBC, it took the AT&T name, capitalizing on its history and keeping the desired single letter symbol).
|NYSE "behind the dot" or Nasdaq 5th-letter codes and other special codes|
|A - Class "A"||K - Nonvoting (common)||U - Units|
|B - Class "B"||L - Miscellaneous||V - Pending issue and distribution|
|C - Continuance - or Nasdaq exception||M - 4th class - preferred shares||W - Warrants|
|D - New issue||N - 3rd class - preferred shares||X - Mutual fund|
|E - Delinquent SEC filings||O - 2nd class - preferred shares||Y - American Depositary Receipt (ADR)|
|F - Foreign||P - 1st class preferred shares||Z - Miscellaneous situations|
|G - First convertible bond||Q - In bankruptcy||Special codes|
|H - 2nd convertible bond||R - Rights||.PK - A Pink Sheet, indicating over-the-counter|
|I - 3rd convertible bond||S - Shares of beneficial interest||SC - Nasdaq Small Cap|
|J - Voting share - special||T - With warrants or rights||NM - Nasdaq National Market|
The most prevalent standard used for international trade is the International Securities Identifying Number (ISIN). An ISIN uniquely identifies a security. Its structure is defined in ISO 6166. Securities for which ISINs are issued include bonds, commercial paper, equities and warrants. The ISIN code is a 12-character alpha-numerical code that does not contain information characterizing financial instruments but serves for uniform identification of a security at trading and settlement.
Securities with which ISINs can be used include debt securities, shares, options, derivatives and futures. The ISIN identifies the security, not the exchange (if any) on which it trades; it is not a ticker symbol. For instance, Daimler AG stock trades on twenty-two different stock exchanges worldwide, and is priced in five different currencies; it has the same ISIN on each, though not the same ticker symbol. ISIN cannot specify a particular trade in this case, and another identifier, typically the three-letter exchange code, will have to be specified in addition to the ISIN. The SEDOL board of the London Stock Exchange is currently revising their own standards to address this issue.