1913-21 Watermark Crown over Double-lined A Thin Paper 4d Carmine and Pale Green variety 'Watermark Sideways' lower left corner block of 4 superb MUH, including variety 'Retouch to Solid Shading at Back of D' (R10/1). A remarkable combination of rare watermark variety with major plate flaw. The only recorded mint block of 4 (the only larger mint multiple being the block of 6), and a very important piece from this issue. BW D101a/(VP)i, cat AU$6000++