After Constantine, the Chi-Rho became part of the official imperial insignia. Archaeologists have uncovered evidence demonstrating that the Chi-Rho was emblazoned on the helmets of some Late Roman soldiers. Coins and medallions minted during Emperor Constantine's reign also bore the Chi-Rho. By the year 350, the Chi-Rho began to be used on Christian sarcophagi and frescoes. The usurper Magnentius appears to have been the first to use the Chi-Rho monogram flanked by Alpha and Omega, on the reverse of some coins minted in 353. In Roman Britannia, a tesselated mosaic pavement was uncovered at Hinton St. Mary, Dorset, in 1963. On stylistic grounds, it is dated to the 4th century; its central roundel represents a beardless male head and bust draped in a "pallium" in front of the Chi-Rho symbol, flanked by pomegranates, symbols of eternal life. Another Romano-British Chi-Rho, in fresco, was found at the site of a villa at Lullingstone (illustrated). The symbol was also found on Late Roman Christian signet rings in Britain.