Why are there letters on these girls' foreheads??

The images above are two of dozens of young girls, each of whom has letters written on her forehead. The pictures were taken between 1959 and 1969 and were found without attribution as to source or purpose. Is this part of a medical study by a dermatologist or plastic surgeon?? Despite hundreds of comments at the website and years of followup, no one has come up with a definitive answer. The pictures are posted at Swapatorium: A Journey Through Junkland. After you scroll through the photos, I think you'll inevitably be drawn to the discussion thread below...