You have to always remember Ford was in it to make money. It is very difficult to put hard dates on changes. There were three assembly plants building Mustangs, typically the plant would use all of the old inventory before switching to the new. It just makes sense, but in a factory setting I can see a pile of new quarters getting set on top of the old ones. Then you some cars built with the surface reflector and days later when the old quarters were use you got some more inset reflectors. If it is within a week or two, I say it is ok.@CALIF GIRL You bring up a good question. I have looked at some of the records I have with cars built around both of these cars. I am finding images that support Feb 19th build date have both bolted on reflectors and recessed.