An electronic market for trading of securities includes a plurality of client stations for entering quotes for securities and a server process that receives quotes from the clients, aggregates the quotes and causes a total of all aggregated quotes to be displayed for a plurality of price levels on the client systems. The market uses a graphical user that depicts aggregated quotes in an aggregate window a plurality of price levels of a product traded in the market. The market also includes processes to handle lock/cross market conditions, match-off of order flow and provides a central quote/order collector that interfaces to disparate order delivery systems to minimize dual liability of market makers.