From one of the most detailed sets ever, celebrating Harrison as the inventor of the marine chronometer, the 28p shows the escapement, remontoire and fusée of his marine timekeeper No4 in all its intricate glory. 

Made in 1759, this allowed navigators to work out their longitude wherever they were, boosting global exploration and thus the British Empire. Clearly, it was also a thing of beauty.

Design: Howard Brown.

Printing: offset litho by Questa.