Scott 157, 178 and 183 - There is a very light amount of color joining
the line and ball to the left of "U.S." Since it is widely
held that the "secret" mark does not appear on all Continental
printings, this stamp must be
distinguished by the color. The Continentals are nearly always a
brown or dark brown. Scott 178 and 183 are of course orange and
should not present a problem, and in fact may provide an excellent way to
get a feel for the secret mark, since they MUST have the mark.