1909-10 Watermark Crown over Double-lined A Thick Paper 10/- Rose-red and Green with CA monogram with very light and indistinct cancel, showing marginal watermark letters 'RA' indicating the monogram to be positioned under Stamp 10/10, contrary to the BW catalogue statement. Very fine without gum and the only recorded example, making this arguably the rarest monogram of Australian Commonwealth. A major postage due rarity, grossly undercatalogued by BW at AU$3500