The 669 is a second generation gun, as opposed to the current third generation. It is most similar to the third generation 6906 in size. It should have a 3.5 inch barrel and 12 round magazine - both shorter than the full-size guns by about a half inch. Most noticeabley, the sights and grips are different than the 3rd generation guns. I think there might be some internal safety differences as well.