Whatever reason motivates you to start walking west, when you reach Compostela you are entitled to wear the scallop shell, the universal insignia of a Santiago pilgrim.
These days, when most pilgrims only walk west and then take modern transportation home from Compostela, people put on the shell when they start out. Medieval pilgrims liked insignia: pilgrims returning from Jerusalem brought palm branches, and were known as Palmers, while those returning from Rome wore the crossed keys of St. Peter, and were called Romers.

How the relationship between the shell and the Santiago pilgrimage evolved is not entirely clear, but it started early. One theory is that because Compostela lies so close to the ocean and scallops are common on the Galician coast, early pilgrims could easily gather the shells and take them back home. Already before our Christian calendar the Roman legions marched to Finisterre (the end of the world) at the Coast of the Dead to see the sun sink into the underworld. They came back with a shell, to prove their rebirth. Think of "The birth of Venus" painting by Boticelli, where the goddess of Love is on the half shell. Yummy. Read the shocking story of Venus' birth .

Another version says that one of the earliest of St. James's miracles was his rescue of a knight who had fallen into the sea. When the knight arose from his watery grave, he was covered with cockle shells, and thus they became linked with Santiago.

You will see the shell everywhere, from a medieval gravestone in Roncesvalles to the myriad statues of Santiago Peregrino. Wearing it identifies you as a member of the special confraternity of pilgrims to Compostela.