I was in Muscat from 1976 to 79 and all the Gulf Air aircraft were A40 registered by then. Also all British built aircraft , VC-10s, BAC 1-11s, Skyvans and Islanders.
And SOAF was mostly British, Viscounts, BAC 1-11s, Skyvans, Islanders, Hunters, Strikemasters, Jaguars. The only non British were the Bell helicopters, 205s, 206s, and 212s. The DHC Caribous departed soon after I arrived and the Beavers had left a few months earlier.
Sorry for the thread drift.