The following reply received from the researcher-
"C9 is part of our long term study on the Isle of May. She is
28 years old and has been breeding regularly on the Isle of May since at least
1992." I HAVE BEEN TOLD THAT MANY YEARS AGO THE RESEARCHERS ACTUALLY BRANDED THE SEALS (JUST LIKE CATTLE) THANKFULLY THIS HAS BEEN REPLACED BY PLASTIC TAIL TAGS.