Could anyone please clarify the meaning of this term in the following context?
(It's about Hollywood, young actors and actresses)
"But according to many people in the entertainment industries, their identical good looks are just not a problem. Nothing sells better than a perfectly proportioned 17-year-old blank slate."
(Presumably the origin of the phrase refers to this sort of 'slate':http://eheritage.statelibrary.tas.go..._00148_1_w.jpg
[not to be confused with this sort: - http://www.funfanatics.co.uk/images%...250%5B1%5D.jpg - excuse the silliness, I was thinking of the context you had in mind]).
It's possible that the term 'blank slate' was a 'translation' of the Latin tabula rasa (with a change to the technology underying the writing system). A tabula was a board covered with wax; you wrote on it using a stylus; and if you wanted to start again from scratch you made it a tabula rasa (think of 'razor'). This expression is still used, with the same figurative sense as 'blank slate'.