A miniature sanctuary in a cylindrical green Bakelite case, a souvenir of Saint Joseph's Oratory as indicated by the slightly erased inscription. Also called "Porta Saint", these small pocket altars were used in particular by soldiers from the late 1800s until the First World War to protect themselves during the war. Even today, many Catholics carry them, often hand-made with their favorite saints, to protect themselves from evil.
This one includes the silver plated figurine of Saint Joseph and the baby Jesus (inscription France), as well as a miniature rosary with small beads in yellow seed beads. 1 bead missing. Heart representing the miraculous medal, and crucifix with the body of Christ.
To understand how to pray the Catholic Rosary, it's here (French): https://www.prierlechapelet.com/pages/comment