GSM Feb 1960: Gulf High Values (Castles) Types I and II printing and issue date details. GSM March 1960: More variations in High Values (Castles) – Muscat and Bahrain. GSM July 1960: Persian Gulf QEII ½ anna “floating fraction” overprint. GSM Sept 1960: Muscat 2R (Castles), De la Rue printings.