1857 Pearson Hill First Experimental Machine Cancellation. A small envelope bearing 1857 1 d rose-red issue addressed to Edinborgh, being tied by a superb strike of the Pearson Hill experimental double datestamp with code M (morning duty) dated for SP 17 57, and bearing on reverse a mirror image of this mark. Small filing creases otherwise fine, and a great rarity being one of only three known examples on full cover.