From The Manufacturer/Wikipedia/People Smarter Than Us:
New for 2010, Smith & Wesson will offer machine-engraved firearms from our Custom Engraving Shop. This new technology utilizes a diamond-tipped tool that etches the design into the surface of the firearm and produces a very clean and sharp hand-engraved appearance. Our initial machine-engraved firearms include two small frame revolvers, the classic Model 29 and a Walther ® PPK/S.