I can't tell you the ruler, but it does look like a genuine 1/4 dinar of the Fatimids. The
reverse (right image) will tell you the ruler that made the coin. The
obverse (left image) seems to have been
standard on
Fatimid 1/4 dinars and matchs the images in Marsden's
Numismata Orientalia Illustrata. Most likely this coin was minted by al-Mustansir, since
his coins are the most common, but I really don't know.