 Double transfers and inverted centers occur in nearly all the different denomination designs.By 1875 the Internal Revenue awarded the contract to print for revenue stamps to the National Bank Note Company who prepared a second series of proprietary stamps.The new revenue stamps are commonly referred to as the "second proprietary issue," and occur in 1-cent, 2-cent, 3-cent, 4-cent, 5-cent, and 6-cent denominations.