1921 Abolition of Slavery Unissued Sixpence. Die Proof. Carmine and green on wove paper (76x64mm.) showing guide crosses; a little stained though exceptionally rare with only two examples believed known. Photoprovenance:. Byron R. Cameron, November 1974 (Image1)

Est. £2,000-2,500

1921 Abolition of Slavery Unissued Sixpence. Specimen Stamps. Watermark MCA overprinted "specimen" (D12) reading up, fine mint. S.G. 90s, £900. Photo (Image1)

Est. £300-400

1921 Abolition of Slavery Unissued Sixpence. Specimen Stamps. Watermark Script CA overprinted "specimen" (D12) reading down, fine mint. S.G. 91s, £750. Photo (Image1)

Est. £250-300

1921 Abolition of Slavery Unissued Sixpence. 1922 (c.) Imperforate Printer's Samples. Yellow-green and violet, handstamped "specimen" (DS1) diagonally at upper left corner. Photo (Image1)

Est. £250-300

1921 Abolition of Slavery Unissued Sixpence. 1922 (c.) Imperforate Printer's Samples. Yellow-green and violet vertical pair, both handstamped "specimen" (DS3) and affixed to piece of brown card numbered "16". Photo (Image1)

Est. £500-600