HEJAZ: al-Husayn b. 'Ali, 1916-1924, AE ¼ ghirsh (piastre), Makka al-Mukarrama (Mecca), AH1334 year 6, KM-22, this is one of the two rarest coins of Hejaz (the other is the ½ ghirsh dated AH1334 year 8), with the clear Arabic number "6"; most examples are either 6 over 5 or 5 over 6 (to correct year 6 to year 5), still extremely rare, environmental damage (actually very little damage), PCGS graded EF details, RRR.
There are no examples listed on either CoinArchives or Zeno. Only one has been graded by PCGS and two by NGC.
Estimate: 3,500-5,000 USD