The use of the red dot centred US roundels on Mustang Mk.I destined for delivery to the RAF, was the temporary application of US marking for conduct of test flights within the USA OR for the couple of aircraft retained by NAA for flight test and development work in the USA - these are the ones most often that have shown up in various publications. Also some instances where applied for NAA publicity photographs. Use of US insignia without the red dot centre seen after Japan attacked Pearl Harbor and generally used for flight testing of RAF aircraft over the USA, particuarly US west coast plants, to avoid issues with the red centre section of RAF roundels being mistaken for Japanese national markings. From what we have been able to find for aircraft destined for the RAF, the temporary US markings were placed over the top of the RAF markings for the duration of flight testing and then removed once flight testing completed and aircraft accepted by BPC/RAF representative at the factory. So when they were crated they carried RAF markings. The problem that arose for the Mustang Mk.I and Mk.IA in the UK after arrival with incorrect placement of the fuselage roundel and incorrect sizing of wing top and bottom roundels, was largely overcome as a part of the repainting process required to change the c&m from temperate scheme with early national markings as delivered by NAA, to the then required RAF day fighter scheme with later national markings in use by the time the aircraft shipments arrived in the UK. NAA had not had issues with RAF style roundels on their earlier and subsequent production blocks of Harvards for the RAF and RCAF - bright trainer yellow not being as menacing a camouflage, but there was a period where Harvards did have US markings applied over RAF markings for test flights or delivery flights from NAA factory to Canadian border.