My very first revolver was a very early Blackhawk flat top in .44 Magnum (Ruger brought out their .44 Mag revolver before S&W did). As I remember it had a 4-digit SN. It was also the beginning of reloading for me, using a .44 Lee Loader. In the late 1960s I very foolishly sold it to a friend because I wanted something different, and also because the Blackhawk was so brutal to shoot with full power .44 Mag loads. One of the many guns I wish I had kept.