The Relic Crucifix.
The Relic Crucifix is considered a third class relic because of the relic "dirt" in the receptacle at the foot of the cross. The dirt is gathered at the Catacombs of Christian Martyrs in Rome, Italy and mixed with adhesive so it will not fall out of the cross. Note that we are not selling the relic, but the receptacle for it which is the crucifix on your rosary.
The dirt is gathered for the manufacturing company from different catacombs in Rome which were known to have burials of Christian martyrs and popes, some of whom were later brought to sainthood. An example of such catacombs is the Catacombs of St. Callixtus. This was a cemetery of the Church of Rome in the 3rd century AD. Around half a million Christians were buried here, among them many martyrs and 16 popes.
Other examples are the Catacombs of Marcellinus and Peter, the Catacombs of St Domitilla, and the Catacombs of St Sebastian.
The photo below displays the other symbols on this Relic Crucifix.