Liberia, 1906, 15¢ Purple & Deep Green, Centered Inverted. Block of 4, o.g., small hinge remnant at top, never hinged at bottom, deep rich color, very fresh, F.-V.F., believed to be one of the rarest 1906 Inverted Centers known with only one sheet of 20 ever found, this being the only known block that still exists. Scott No. 105a  $700 for hinged singles. $0 (Image)