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
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.