Below you will see the experiment stimuli. The naming structure tells you what you need to know.
US = unsymmetrical - that is, this is an individual face with no averaging
S = This is a face averaged with three individual faces
F = Female; M - Male; B = Black; W = White
For example, SBF_1, is a face averaged from USBF_1, USBF_2, and USBF_3. SBF_2 is a face averaged from USBF_4, USBF_5, and USBF_6. And so on for the others.