The Model 6906 is actually the compact version of the Model 5903, since both have an alloy frame and stainless slide. (As mentioned, the Model 5906 has a steel frame.) The Model 6906 is the Third Generation version of the original Model 669, Smith's first double-stack compact pistol.

Both the Model 669 and Model 6906 will accept any 5900 series magazine of any capacity. Magazines that hold more than 12 rounds will extend below the grip frame of the pistol. Smith offered a 20-round magazine for the Model 669/6906.