Early Byzantine coins continue the late Greco-Roman conventions: on the obverse the head of the Emperor, now full face rather than in profile, and on the reverse, usually a Christian symbol such as the cross, or a Victory or an angel (the two tending to merge into one another). The gold coins of Justinian II departed from these stable conventions by putting a bust of Christ on the obverse, and a half or full-length portrait of the Emperor on the reverse. These innovations incidentally had the effect of leading the Islamic Caliph Abd al-Malik, who had previously copied Byzantine styles but replacing Christian symbols with Islamic equivalents, finally to develop a distinctive Islamic style, with only lettering on both sides. This was then used on nearly all Islamic coinage until the modern period.