Britain's most spectacular commemoratives, No23: 1999 Patients' Tale 20p

Commemorating Dr Edward Jenner’s invention of a defence against smallpox in the 18th century, this stamp cleverly alludes to a folkloric tale and involves a very subtle optical illusion.

It was from the knowledge that milkmaids did not contract smallpox if they had previously suffered from cowpox that Jenner developed his ‘vaccine’ (the word comes from the Latin for ‘cow’) containing material from cowpox sores. 

Accordingly, the design shows a caricature of a Friesian cow, whose black and white markings contain a silhouette of the doctor vaccinating a child. A milkmaid carrying a yolk and buckets completes the scene.

Design: Peter Brookes.

Printing: gravure by Questa.