Really good and interesting information of the Boss's SAS rank slides
but to bring the thread back to the original question, I attach two further photos.
One of a Guards officer in the 1990s wearing a blue frock coat with the standard colour SAS wings, rather than an bullion version, and one of the CDS in 1997 wearing Full Dress with bullion SAS wings. which have a blacked backing rather than red, and which are the gold chute and silver wings variant.
My point is that there appears to be no discernible rules with these wings.....