I took the red dot off, and found out it is the old square style sight assembly. Also figured out it is a .146 blade height and S&W no longer stocks the item. I found a few on ebay and gunbroker, but I don't want to put somebodys old rusty junk on my beautiful gun. Does anybody know who makes replacement rear sight assemblies, other than Bowen? ($125 and drill it yourself sounds expensive to me)