But the question is, who is to say when a priest blesses a medal it suddenly has these specific properties, and on what authority did they come up with the list ?
The list seems to be based on the prayer used by the priest in the name of the Church to bless the medals.
I don’t know if the wording of this particular blessing is found in the current Roman Ritual (Book of Blessings) but here is an example at least from the past.
31. BLESSING OF MEDALS OF ST. BENEDICT
(Formerly reserved to the Order of St. Benedict)
The priest who is to bless the medals of St. Benedict says:
P: Our help is in the name of the Lord.
All: Who made heaven and earth.
I cast out the demon from you, creature medals, by God the Father
almighty, who made the heavens and the earth and the seas and all
that they contain. May all power of the adversary, all assaults
and pretensions of Satan, be repulsed and driven afar from these
medals, so that they may be for all who will use them a help in
mind and body; in the name of the Father + almighty, of Jesus +
Christ, His Son, our Lord, of the Holy + Spirit, the Advocate,
and in the love of our Lord Jesus Christ, who is coming to judge
both the living and the dead and the world by fire.
All: Amen.
Lord, have mercy. Christ, have mercy. Lord, have mercy. Our
Father (the rest inaudibly until: )
P: And lead us not into temptation.
All: But deliver us from evil.
P: Save your servants.
All: Who trust in you, my God.
P: Let us find in you, Lord, a fortified tower.
All: In the face of the enemy.
P: The Lord will give strength to His people.
All: The Lord will bless His people with His peace.
P: Lord, send us aid from your holy place.
All: And watch over us from Sion.
P: Lord, heed my prayer.
All: And let my cry be heard by you.
P: The Lord be with you.
All: May He also be with you.
Let us pray.
Almighty God, lavish dispenser of every good, we humbly ask that
by the prayers of St. Benedict you pour out your blessing + on
these sacred medals, impressed with letters and signs ascribed to
you. Let all who will wear them with hearts intent on good works
deserve to obtain health of mind and body, your holy grace, and
the indulgences that have been granted to us. And may they escape
by your merciful help all attacks and wiles of the devil, and
finally appear in your presence sinless and holy; through Christ
our Lord.
All: Amen.
Let us pray.
Lord Jesus Christ, who willed in redeeming the whole world to be
born of a Virgin, to be circumcized, rejected by the Jews,
betrayed with a kiss by Judas, bound in chains, crowned with
thorns, pierced with nails, crucified between robbers, wounded
with a lance, and to die at last on the cross; I humbly ask, by
this your sacred passion, that you expel all attacks and wiles of
the devil from the person who devoutly calls on your holy name,
using these words and signs ascribed to you. May it please you to
lead him (her) to the harbor of everlasting salvation, you who
live and reign forever and ever.
All: Amen.
May the blessing of almighty God, Father, Son, + and Holy Spirit,
come upon you and remain with you forever.
All: Amen.
The priest sprinkles the medals with holy water. (
source)