0 . ▁In ▁addition ▁to ▁this , ▁the ▁Um ay y ad ▁government ▁began ▁to ▁mint ▁its ▁own ▁co ins ▁in ▁Dam asc us , ▁which ▁were ▁initially ▁similar ▁to ▁pre - ex isting ▁co ins ▁but ▁evol ved ▁in ▁an ▁independent ▁direction . ▁These ▁were ▁the ▁first ▁co ins ▁mint ed ▁by ▁a ▁Muslim ▁government ▁in ▁history . ▁Gold ▁co ins ▁were ▁called ▁din ars ▁while ▁silver ▁co ins ▁were ▁called ▁dir h ams . ▁ ▁Central ▁di w ans ▁To ▁assist ▁the ▁C ali ph ▁in ▁administration ▁there ▁were ▁six ▁Bo ards ▁at ▁the ▁Centre : ▁Di wan ▁al - K har aj ▁( the ▁Board ▁of ▁Re venue ), ▁Di wan ▁al - R asa ' il ▁( the ▁Board ▁of ▁Cor respond ence ), ▁Di wan ▁al - K hat am ▁( the ▁Board ▁of ▁Sign et ), ▁Di wan ▁al - Bar id ▁( the ▁Board ▁of ▁Post s ), ▁Di wan ▁al - Q ud at ▁( the ▁Board ▁of ▁Justice ) ▁and ▁Di wan ▁al - J und ▁( the ▁Military ▁Board ) ▁ ▁Di wan ▁al - K har aj ▁The ▁Central ▁Board ▁of ▁Re venue ▁admin ister ed ▁the ▁entire ▁fin ances ▁of ▁the ▁emp ire . ▁It ▁also ▁im posed ▁and ▁collected ▁tax es ▁and ▁dis b urs ed ▁re venue . ▁ ▁Di wan ▁al - R asa ' il ▁A ▁regular ▁Board ▁of ▁Cor respond ence ▁was ▁established ▁under ▁the ▁Um ay y ads . ▁It ▁issued ▁state ▁miss ives ▁and