I own one of the newer production Walther PPK/S .22s, which the one you're seeing most likely is. Basically, if it has a threaded barrel, Matte Black or Nickel finish with black controls, then it's a modern iteration. Classic models from decades past are almost always Blued, save for a few old military contract or confiscated versions which were parkerized, plated, or coated afterwards.
There is a ridiculous amount of biased and misinformation regarding the newer (2013 or later) PPK/S .22, which I will go over here. (Settle in, this is going to take awhile to cover...)
* It's not really a Walther
As of 1993, Walther is a subsidiary of Umarex, a company which mainly produces Airsoft and Rimfire Replica Firearms. The Walther PPK/S .22 is produced at the Umarex factory, but bears the Walther banner and makes no reference to Umarex, which leads folks to believe that it's an Umarex manufactured gun using the Walther branding.
However, what folks fail to understand is that since Umarex owns Walther and has for decades, some of their firearms have been manufactured at the Umarex plant. Also, while fanboys love to use Umarex as a scapegoat for every time Walther turns out a pistol which isn't perfect or happens to have issues down the line, Umarex is in fact not a completely separate company who manufacturers low quality firearms while Walther continues to inexplicably make high quality firearms in spite of being a subsidiary of Umarex. In short, the Walther PPK/S .22 is indeed a Walther product, and even if it wasn't, that wouldn't make the PPK/S .22 a poor quality firearm. Umarex makes plenty of other officially licensed high quality Rimfire Replica firearms which are merely cheaper in price on average compared to Walther because Walther mostly makes firearms for self-defense or police, ergo more expensive materials are required because they're chambered in 9mm Luger as opposed to .22LR.
* It's made of pot metal
Due to a mixup on Walther Arms USA's website during the launch of the new production PPK/S .22 which erroneously listed the slide/frame material as "Zinc Diecast" many folks have turned their nose up at it and continue to do so to this day, citing said misinformation.
However, the Walther PPK/S .22 is in fact made of some sort of proprietary alloy which Walther Germany claims isn't "Zinc Diecast" at all. Presumably, it's the same Aluminum alloy they use for the 1911 .22 and PPQ .22 which were introduced around the same time.
* It's not really a PPK/S
Perhaps the most ignorant and demonstrably false bit of misinformation surrounding the PPK/S .22 is also sadly among the most prevalent. According to some, (namely purists) the Walther PPK/S .22 isn't really a PPK at all but rather a variant of the Walther P22 dressed up as a PPK/S.
However, this is a gross exaggeration at best. While the modern iteration of the PPK/S .22 has some minor internal differences from the classic Walther PPK/S which it shares in common with the P22, to say they're internally the same firearm is completely ridiculous. The PPK/S .22 only has three direct similarities with the P22, the threaded barrel, barrel shroud, and the barrel nut which secures it.
* TL;DR
Pretty much everything negative said about the modern iterations of the Walther PPK/S .22 are complete misinformation perpetrated by ignorant people who are just repeating what they've read online. They make excellent little plinkers with a touch of style and will please anyone besides purists who can't get past minor aesthetic differences from the classic models which typically cost 3x the price. You get what you pay for.