The first stainless Walther PPK and PPK/s models were made for Interarms by Ranger, in as I recall, Alabama.
The last made got a bad reputation for quality problems, but most of these were fine quality pistols.
It was after Interarms went out of business that S&W took over the production and they made some small changes, notably the extended tang on the frame.
For some reason they made a minor change in the frame that prevents using older type grips on the S&W model.
S&W had quality problems and had at least one recall.
Most people will call the S&W the lowest quality of the American made PP series pistols.
The Walther PP series are sort of the 1911 of .380 autos. It's the .380 that all others are judged by, and no one ever quite managed to pack so many features in such a small package.
It is heavy by today's plastic standard, but the Walther still delivers the goods on demand.
These guns seem to "like" grease as a lubricant on the frame and slide rails, and outside of the barrel.
Before heading to the range, clean the factory lube out and apply fresh lube, with grease on the above areas.
As with all PP series pistols, the double action trigger is HEAVY and there's nothing much to be done but get used to it. Lighter springs tend to cause reliability problems.
Happily, once you get used to the DA trigger by practicing with it, you no longer notice it.