Using a bit of guesswork, J.P. Morgan analyst Phil Cusick calculates that Verizon Wireless’ pre-sales of the iPhone 4 may have topped 500,000 units. In a note to investors on Monday, Cusick cited information contained within an earlier press release from Verizon Wireless to take a somewhat educated stab at pre-order totals. According to Verizon, pre-sales of the iPhone 4 broke the carrier’s previous first-day sales record in just the first two hours of availability. Cusick states that the prior record for single-day handset sales was 100,000 units, set by the Motorola DROID last November. Using that information along with the knowledge that Verizon Wireless and Apple continued to take pre-orders for another 15 hours before pulling the pre-order pages from their respective websites, Cusick estimates that over a half-million orders were placed. Cusick believes that Verizon’s iPhone 4 will go on to beat the DROID’s opening day, opening weekend and opening week sales totals, and he estimates that first-quarter iPhone sales will easily top the DROID’s fourth-quarter performance of 1.6 million units, as well.