Anyone have any info as to the date of introduction of the (4) position adjustable front sight used on a few S&W models? I know I have seen some 686's equipped with this particular sight plus I own the M29 Silhouette 10 5/8" bbl that was first reviewed in the April 1983 Edition of Shooting Times that wears this sight. I am trying to find any other articles or literature related to this. Please advise....thanks, Jerry (Gerrard)