I happen to own one. The 669 is S&w's 9mm compact 2nd gen pistol. Stainless slide alloy frame. Was shipped with either 12 rd or 10 rd mags depending on which side of the Brady bill they were but will accept any 2nd or 3rd gen double stack mag. Iirc production dates were 1984-1988. Your s/n compared to mine I think indicates an extremely late build. The 669 incorporated some of the advancements of the Asp and devel customs, cut down grip and slide etc...
I love mine. The only reason I don't carry it is I stepped up to a m&p45c. It's still my nightstand gun though. Holsters are limited but high noon can do them. Id probably OC it if I had a reason to. It's old school 80's cool.
Never Forget 9/11/01