Gold and micromosaic brooch of the Chi-Rho.
Measuremnt : 23 mm in diameter
The Chi Rho is one of the earliest forms of christograms, formed by superimposing the first two (capital) letters—chi and rho (ΧΡ)—of the Greek word ΧΡΙΣΤΟΣ (Christos) in such a way that the vertical stroke of the rho intersects the center of the chi.
The Chi-Rho symbol was used by the Roman Emperor Constantine I (r. 306–337) as part of a military standard (vexillum). Constantine’s standard was known as the Labarum.
The so-called “Chrismon of Saint Ambrose” (Chrismon Sancti Ambrosii), on display on the eastern wall of Milan Cathedral, a Chi-Rho combined with Alpha and Omega in a circle. According to Landulf of Milan (12th century), it was used by Saint Ambrose to introduce the catechumens to the mysteries of the Christian faith (whence it was called “oracle” or chresmos of St. Ambrose, written by Landulf as crismon, whence the later New Latin term for the Chi-Rho symbol).
The Chi-Rho with a wreath symbolizies the victory of the Resurrection.