"Possible flag" of the Hafsid dynasty in the 15th century (unreferenced).

The relevant Flags of the World entry shows no evidence of this double crescent design, presenting instead various versions of flags with a single upward-pointing crescent.
self-made (based on http://www.hukam.net/family.php?fam=44 and http://www.allstates-flag.com/fotw/flags/tn-hist.html#14th)
DrFO.Jr.Tn