I a looking to buy a Walther P99 in .40 S&W. As I look around I am finding one marked QPQ. I found the P990 which is the double action version, what is a QPQ?
Stands for Quench-Polish-Quench, a clear Tenifer finish as opposed to the black. Some refer to it erroneously as Stainless. It is not, but has that appearance.
Just make sure you get a German one, identified by the proof marks on the right rear of the slide. To my knowledge, the S&W made slides were all blue, so a QPQ should be a safe bet.