The photo above is of a passport with stamps. This passport comes with no stamps, you collect them when you walk.
Note that this passport comes free with many of my Camino Guide books.
Also have a look at the Pilgrim Passport Sleeve to protect your passport.
The credential has place for 54 stamps. This is the Official Pilgrim Credencial (Pilgrims Passport) issued by the Pilgrims Office in Santiago de Compostela.
Walk the Camino and collect stamps along the way. Once at the Pilgrims Office in Santiago, show this document and you will receive your Compostela.
The credential is required for pilgrims using public albergues.