"On a November day in 1925 an elderly woman entered Richard Smith and Sons Watchmakers and Silversmith in the small seaside town of Scarborough, in northern England. She was reluctant to give her name but let slip in conversation that her mother had once been a member of the aristocratic Cayley family from the nearby Brompton-by-Sawdon Estate. She offered a selection of blackened silver oddments and broken jewelry that Smith, feeling a little sorry for the woman, reluctantly purchased.

Some time later, whilst idly cleaning one of the pieces - a silver disc about the size of a British shilling - Smith discovered an engraving dated “1799”. On one face was a simple, but obscure trigonometric design; on the other was what appeared to be a covered boat with a curiously elaborate rudder. Underneath it were the initials “GC” which Smith immediately recognized as those of Sir George Cayley, the Brompton-by-Sawdon Baronet who had died 1857.

The disc was, in fact, both the design for an airplane and the description of the forces by which a wing can fly. This small coin documented both the scientific principle for and the practical application of heavier-than-air aviation fully a hundred years before the Wright Brothers’ historic flights at Kitty Hawk, North Carolina."

- The Man who Discovered Flight: George Cayley and the First Airplane (Prologue)