There are 5 designs of indicia whose face value is thirty-three cents, each of which is distinctive enough that it can be identified by examining the images below.

U.S. flag on yellow pole	design U184	You have identified design #U184 diagnostic for Scott #U642 (printed in yellow, blue, and red on white paper).
U.S. flag on blue pole	design U184a	You have identified design #U184a diagnostic for Scott #U643 (printed in blue and red on white paper).
Love	design U185	You have identified design #U185 diagnostic for Scott #U644 (printed in violet on white paper).
Bust of Abraham Lincoln	design U186	You have identified design #U186 diagnostic for Scott #U645 (printed in blue and black on white paper).
Great Seal of the United States	design UO37	You have identified design #UO37 diagnostic for Scott #UO89 (printed in blue and red on white paper).