Nice 669! There was a recall on the gun (manual safety) years ago. I see by your serial # that yours was in the affected grouping. Go to FirearmsID.com- An Introduction to Forensic Firearm Identification and look under the heading "Firearm Recalls & Warnings Index". I had to send mine back, no biggee.
Also, several were affected by frame failure. There was a post started on 12/2011 on this forum (S & W Semi-Auto Pistols)with pics.
Now the good news: you got a great deal on yours! On mine, the trigger pull in the SA mode is light & predictable. Very nice shooter! Never sell it.