So the Muslim forces used a number of shields of varying shapes and material. Based on your description, I believe you are describing a Dhal shield. Dhal shields were originated from South Asia but they were also made in Persia where they were called Sipars. Although they were often made of whicker (kalkan) (Note: Kalkan refers to the whicker material, not the shield type. I attached a link that shows a shield very similar in style to the one you described, it’s a Dhal style but it is made of Kalkan) they were also made of metal- mostly steel or iron and could be inlaid with precious metals and stones. They are a type of buckler shield and often feature the 4 distinct rivets/bosses that fasten the handle to the shield. Heres a paper specifically on Islamic armor to further guide your studies.