A well centered and very fine mint NH lower right blank corner block of the 15c deep rose lilac Bylot Island stamp from the 1967-1973 Centennial Issue, with Winnipeg tagging and a plastic flow doubling of the "15" on the two right stamps. The doubling appears as a vertical line just to the left of the "1" and the vertical stroke of the "5" and on the inside. The two right hand stamps are normal examples that show clear doubling. Horizontal wove paper with no visible mesh or ribbing and smooth creamy dextrose gum with a semi-gloss sheen. Under long-wave ultra violet light the paper gives a dull fluorescent greyish white reaction, with very, very few medium and high fluorescent fibres visible in the paper. This is an unlisted paper type, which is closest to what Unitrade would call DF-fl. Winnipeg tagged with three sets of 8 mm bars, of moderate strength, being clearly visible to the naked eye and spaced 29 mm & 27.5 mm apart. The ink colour under UV is also deep rose lilac. Unitrade values a VF-75 NH block with two variety stamps at $300, The block offered here grades VF-80 as follows: Margins/centering: 50/70 Paper freshness: 5/5 Colour: 5/5 Impression: 5/5 Absence of visible paper flaws: 5/5 Perforations: 10/10 Note any vertical or horizontal line shown in the scan is the edge of the acetate strip that the stamp was resting inside on the stockcard.