This legend was displayed on some British coinage (silver and half crowns only) between 1902 and 1910 during the reign of King Edward VII. It is not the full text - the rest of the legend, FID: DEF: IND: IMP: (Defender of the Faith, Emperor of India) is on the reverse of the coin.
By long-standing tradition, the legends of ruling British monarchs are rendered in Latin. On coinage, these are abbreviated because of the limited space available. Below, you can find a list of the individual coins that had it on their obverse.