Offset Stamp Identification

h

One method is to gently drag the tip of your stamp tongs across the frame line of the stamp. You will feel a distinct bump on engraved stamps and none on the offset since the ink lies absolutely flat on the offset printed stamps. I am assuming you are referring to the offset printed Washington-Franklins of 1918 of the United States stamps. Other series of stamps I have never had the need to distinguish.