6c Ultramarine & Carmine (C23c). Mint N.H. top plate nos. 21911 and 21951, double "TOP" and registration markers block of ten, with side selvage and comprising the top two rows of the sheet, brilliant colors in these distinct shades, each stamp with light pencil Bloch signature

VERY FINE. AN EXTREMELY RARE MINT NEVER-HINGED TOP PLATE BLOCK OF TEN OF THE 1938 6-CENT ULTRAMARINE AND CARMINE AIR POST ISSUE.

Apart from a complete pane of 50 (which contained one plate block), we have offered only three other plate blocks of Scott C23c since keeping computerized records. Each of those was a block of four. This block of ten, comprising the full top two rows of the sheet is a striking and great rarity.

From our 1981 Rarities sale where purchased by the family of the consignor. Scott value as plate block of four and six singles, without premium for the additional "+" marker positions.

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