The "Medal of the Immaculate Conception" known as the "Miraculous Medal" was designed by the Blessed Virgin herself!
On the Front Side of the Medal Mary is standing as the Queen of Heaven and Earth upon a globe, crushing the head of a serpent beneath her foot.

The year of 1830 on the Miraculous Medal is the year the Blessed Mother gave the design of the Medal to Saint Catherine Labouré.
The back of the Medal, recall the vision of Saint John, in the Book of Revelation (12:1), in which “a great sign appeared in heaven, a woman clothed with the sun, and the moon under her feet, and on her head a crown of 12 stars.”
The Cross symbolize Christ and our redemption and
the bar under the cross a sign of the earth.
The “M” stands for Mary,
and the two hearts represent the love of Jesus and Mary for us.