Just came across this cover. Nothing special other than the distance within the US that this particular cover was carried. Roughly speaking, the mileage between destinations of Oahu, HI and Gloucester, MA is about 5900 miles, which figures to a little more than 1/1000ths of a cent per mile. (7 cents was not a bad price to travel that distance.)

I know that internationally covers can travel a greater distance, but I suspect this is one of the longer distances between US cities.