Twenty years ago (when I was 12), my friends and I always felt that 12 centers were Silver and 15 centers were Bronze. Now I can actually quantify that position. If we are looking at GL/GA #76 as the start of Bronze, due to the human and true to life storytelling and the loss of innocence in comic books...then why don't we go back as far as ASM #96-98. Marvel did it first, they knowingly took on the code, took a risk and they did it with their most popular book! Harry was hooked on something (pills, acid, something) and having flashbacks, a lot earlier than Speedy was. Thats the book(s) that opened the door for everyone else to follow suit and push the envelope.
Jim