begins with basic mint and used stamps (less O3 mint and O8), followed by shades (O1.1 green and O7.1 rose lilac), overprint varieties including last "A" of "Panama" under "L" of "Official" (O1.4, O2.1, O4.1, O5.1, O7.2, and O9.1), and CTO varieties including inverted and vertical, generally fine to very fine, an attractive specialized group