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| blued (imperforated) 1841-54 (ivory head) | ||
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| blued 1854-7 | cream 1856-7 | white 1857-79 |
The blue colour was the result of a chemical reaction between
the paper and the fugative ink introduced in 1841
(made fugative by the addition of prussiate of potash to the red ink).
An ivory head is due to the absence of ink on the head,
so that it appears white on the back of the stamp.