This is the full-page image that you saw when you opened the 1977 Personal Progress book (the "purple book" if you remember it that way), behind a vellum sheet. It's The Annunciation, by John Scott, copyright 1975. On the next page, there's this caption:
"The qualities and virtues sought by young women in The Church of Jesus Christ of Latter-day Saints are exemplified in the lives of many notable women throughout history. Among these is Mary of Nazareth whose mission to be the mother of the Son of God is unique in all history."