Dominica 1968 1c Mint National Day Variety Unlisted Three Overprints

Dominica 1968 1c National Day Mint Marginal Vertical Pair with Only Top Stamp Variety OVERPRINT DOUBLED with THIRD OVERPRINT INVERTED - Bottom Stamp has Normal Overprint. Perfs Reinforced Between Stamps with Part Hinge. Combination of Both Doubled & Inverted Overprints UNLISTED. Gibbons Lists Only: SG 232a Inverted Opt & SG 232b Quadrupled Opt.