Suppoose someone has a reserve bid at 10.00, and is showing only 1000 shares at a time. I then place a bid at the same price, same venue. Once his order for 1000 shares is filled, does my order jump ahead of his?
I believe that the displayed portion of your order takes priority over the undisplayed portion of any other order at the same price on an ECN. I believe displayed ECN orders, at the same price, compete against each other based on time priority, and that undisplayed ECN orders, at the same price, compete against each other based on time priority.