These are witnesses of faith and a sign of veneration of the Holy Mother of God, as well as of trust in her maternal protection. The Church blesses such objects of Marian devotion in the belief that “they help to remind the faithful of the love of God, and to increase trust in the Blessed Virgin Mary.”
The Miracle of the Miraculous Medal: Designed and Revealed by the Blessed Virgin
The Medal of the Immaculate Conception, popularly known as the Miraculous Medal, is unique among all medals.

During the night of July 18-19, 1830, the Most Holy Virgin appeared for the first time to Saint Catherine Labouré, who had been awakened and led from the dormitory to the chapel by her guardian angel.
In the sanctuary, St. Catherine Labouré later wrote:
“I heard something like the rustling of a silk dress, coming from the side of the tribune, close to Saint Joseph’s picture. She alighted on the steps of the altar on the Gospel side, in an arm chair like Saint Anne’s… As I looked up at Our Lady I flung myself close to her, falling on my knees on the altar steps, my hands resting in her knees. That was the sweetest moment of my life.”
Catherine saw Our Lady standing on a globe, with dazzling rays of light streaming from her outstretched hands. Framing the figure was an inscription: “O Mary, conceived without sin, pray for us who have recourse to thee.” Then Mary spoke to Catherine: “Have a medal struck upon this model. Those who wear it will receive great graces, especially if they wear it around the neck.”
The vision then seemed to turn to show the reverse of the Medal: the letter M surmounted by a cross with a bar at its base; below this monogram, the Sacred Heart of Jesus crowned with thorns, and the Immaculate Heart of Mary pierced with a sword.
With approval of the Catholic Church, the first medals were made in 1832 and were distributed in Paris. Almost immediately the blessings that Mary had promised began to shower down on those who wore her medal, and soon all of France was clamouring for what the people referred to as the “Miraculous Medal.” Use of the Medal spread from country to country and now blankets the world. Everywhere, the Medal is still drawing down from God blessings for body and soul.