Kindly check Piet Kaas, 1988. American Malacological Bulletin. Vol. 6 (1): 115-130. Chitons (Mollusca, Polyplacophora) from the Coasts of Oman and the Arabian Gulf.
You could able to compare and check the valves and radular teeth, if you have examined your specimen.
With the photo and the locality,: Acanthopleura vaillantii de Rochebrune. Is very similar to the Caribbean Acanthopleura granulata. In Kaas, P, RA Van Belle and HL Strack. 2006. Monograph of Living Chitons (Vol 6): 269 you can see the A vaillantii photo, is the only specie of the genus in the Oman area.