As bobgee pointed out some pilots enlisted in the RCAF not the RAF so they naturally would be wearing their RCAF brevets. Another interesting thing to note. And this relates to the award of the RAF 1942 badge. Many think this badge was awarded to all the Eagle Squadron members (and others that served in other RAF units). It was an RAF award, so if you had enlisted in the RCAF you were not entitled or awarded the RAF 1942 badge. Many well known Eagle Squadron members were not awarded the badge. Don Blakslee and Jim Goodson among them, as they were RCAF not RAF. Hope this helps.
Hi Scarecrow - My understanding is that ALL American pilots serving with the RAF, regardless of whether they were RAF or RCAF at the time of their transfer to te USAAF in Sept 1942 received the "1942 RAF" breast badge, In fact, there was on on this pilot's U.S. uniform but his sister kept it. All of the U.S. insignia was bullion. Regards....Bobgee