I have no doubt these are genuine, with slight ink misregistration. Looking through 7 covers bearing 3520, I find these 2, note the broken vertical bar of the T in Presorted:


And looking through 13 covers bearing 3770 (the 2003-dated version), I found at least 4 with misregistrations including these 2:


My apologies for the white background, but they are all on cover!