Given that 'blunt' means 'not smart' and that 'mettle' means 'wit; intelligence', I believe that the statement that best paraphrases "What a blunt fellow is this grown to be! He was quick mettle when he went to school" is "This man, who was smart in school, has grown up to be unintelligent".
Silent grief of a loved one babe
The answer is simile because similes uses the word as
example: That man ran as fast as a roadrunner.
A word used to mean 'before'.