Mosaic brooch

Small circular gold brooch with micro mosaic of the image of Chi Rho. Italian Grand Tour ca 1860.

Measurements : 23 mm in diameter
The Chi Rho is one of the earliest forms of the Christogram, formed by superimposing the first two (capital) letters—chi and rho (ΧΡ)—of the Greek ΧΡΙΣΤΟΣ (rom: Christos) in such a way that the vertical stroke of the rho intersects the center of the chi.[2]

The Chi-Rho symbol was used by the Roman Emperor Constantine the Great (r. 306–337 AD) as part of a military standard (vexillum). Constantine's standard was known as the Labarum.