On September 17th, NYSE Regulation issued an information memo regarding September 20, 2013, which was a quarterly Expiration Day for stock and index options and futures products whose settlement pricing is based upon New York Stock Exchange and NYSE MKT opening or closing prices on that day. The information memo reminds members of certain NYSE and NYSE MKT rules and policies regarding opening imbalance publications, entry and cancellation of market-on-close/limit-on-close and closing offset orders, publication of on-the-close imbalances, and printing the closing transaction. NYSE Regulation Information Memo 13-19.