This micro mosaic pin must have been a souvenir of a pilgrimage to the Vatican in Rome long ago. It has been identified as a picture of Pope Pius X, pope from 1903 - 1914.
The brooch is about 1" across, the area around the photo filled with tiny tesserae and the letters ROMA. The brooch is in good condition, with some wear around the c-clasp. There do not appear to be any missing tiles.
Item ID: J-1189