The Miraculous Medal depicting a monogram of the Holy Name of Mary and the Sacred Hearts of Jesus and Mary, surrounded by twelve stars which represent the Twelve Apostles who in turn represent the whole Church.
The Immaculate Heart:
The symbol of the Immaculate Heart , sometimes with a sword piercing it, is in reference to Simeon's prophecy in St. Luke, Chapter 32, Verse 35:
And thine own soul a sword shall pierce, that out of many hearts, thoughts may be revealed.
Other times the Lily replaces the Sword, as it does here.
The Sword is for sorrow, the Lily for purity and joy. Long ago, a circle of thorns used to replace the roses.