See the margin reference note. Josephus says that Samuel’s call to the prophetic office happened when he had just completed his twelfth year (compare Luke 2:42).
Was precious - (or rare) The song of Hannah, and the prophecy of the “man of God” (1 Samuel 2:27 note), are the only instances of prophecy since Deborah. Samuel is mentioned as the first of the series of prophets Acts 3:24.
No open vision - Better rendered, “There was no vision promulgated or published.” (Compare 2 Chronicles 31:5.)