AFAIK, the 4040PD is the only scandium-framed 3rd Gen ever produced, maybe the only scandium semi-auto S&W ever made? I don't know all of the PC models, so maybe there was one in there too.
I do know that it is the only single-stack 40sw designed from a 9mm frame in the 3rd Gen lineup, and that it was one of the last models to be introduced before they shut down 3rd Gen production. It has many features of the TSW series - thicker frame rails, loaded chamber port, setup for decock-only conversion - as well as benefiting from the later advancements in fabrication, with great slide-to-frame fits and smooth triggers.
The 4040 is basically the same size as a 3913NL, making it IMO the most concealable 40sw in the 3rd Gen lineup. 3913 grips, mag springs, base plates, buttplate catch assemblies are all used by the 4040, and most leather 3913 holsters will fit as well. Magazine bodies and followers are specific to the model, but as has been stated, NOS 4040 magazines are still available online. Trijicon offers night sights for it (SA15) and the dual recoil spring setup is the same as the 457/4516/4013TSW (Sprinco also makes great aftermarket spring sets).
Definitely a rare bird and IMO worth picking up. Depending on condition, what comes with it, etc. $600 is not out of line. For a well-used model with one mag, that's a bit pricey, but it would be a fair price for a gently used gun, especially with original box and 2 mags. I've seen used 4040's sell for over $700 and NOS specimens go for close to $1K. As I said, a rare bird.
