Paper varieties viewed under long wave light.
BCP = Bluish coated paper PVA = Polyvinyl alcohol acetate gum
OCP = Original coated paper
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P1, P1mp or P2 - 1/2d Orange brown (Shades), BCP/PVA, two 4.75mm screen 150 B3 phosphor bands, head A1, upright print (Cyls 2, 3)
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P1 Orange brown shade from sheets cylinder 2 [5.2.68] - Deegam PD 1.1.1 - S.G specialised U1 - Stoneham M13 - Concise 723
P1mp Phosphor omitted from sheets cylinder 2 - Deegam PD 1.1.1a - S.G specialised U1a - Stoneham M13a - Concise 723Ey
P2 Pale orange shade from sheets cylinder 3 [?.3.69]