The Holy Shroud of Oviedo
The Sudarium is referred to in John 20:5-8.
The Sudarium of Oviedo, or Shroud of Oviedo, is a bloodstained cloth, 34" x 21", kept in the cathedral of Oviedo, Spain and claimed to be the cloth that was wrapped around the head of Jesus of Nazareth after he died (Head-veil of Christ).
The piece of cloth encased on back of this medal has been touched to the Shroud of Oviedo. I have one of my own and recently I noticed that it has a small red stain, what appears to be blood. At first I thought it was the dome that was stained, but it's actually inside, I was so amazed to see it and for me is a sure sign Our Lord is reminding me of His love.
The new medals all come with just the piece of white cloth and mine was the same way until recently that I noticed the stain.