At the moment, S&W is still the producer of the PPK and PPK/S in the US, although at this point it is winding down and they are just assembling pistols from existing stocks of parts.
My understanding is that Walther/Umarex is expanding their facilities in Ft. Smith, Arkansas and that production of the PP and PPK/S will be moved there. That makes me a bit nervous as Umarex's main influence on Walther has been in reducing the price point by reducing the cost and quality of production. The PPK/S .22 LR is a good example. For a $400 dollar pistol competing with other $400 .22LR reproductions of CF pistols it's not so bad and it follows the PPK/S design in terms of function and operation, with the exception of using a P22 style barrel shroud and barrel liner, and lower cost engineering in the production of the small parts. But it lacks the over all quality, fit and finish of the centerfire PPK and PPK/s pistols made in the past.
Consequently, I'm uncomfortable predicting how any new PPK or PPK/S .380 ACP or .32 ACP pistols would be made. It's also not entirely certain the PPK and PPK/S will stay introduction at all, although I suspect that's the case, or they'd have no reason to end the current arrangement with S&W. If they make them in Ft. Smith, Walther may stay the course with a higher price point, or they may take the Umarex approach and cheapen the manufacture of the design, which would be a really, really bad thing to happen.
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Historically speaking, the PP series pistols break down into several manufacturing classes:
1. Pre WWII pistols made from 1929-1940. These were made in Zella Mehlis Germany, in what became East Germany after WWII.
2. War time pistols made from 1940-1945. These were also Zella Mehlis pistols, but quality and finish started to decline, particularly after about mid 1943 as the war started to turn against the Germans.
3. Post war, Manhurin made PP series pistols. The Germans were prevented from producing small arms until about 1960, so shortly after the war, about 1952, Walther began a partnership with Manuhrin, short for "Manufacture de Machines du Haut-Rhin", located on the Rhine River at Mulhouse-Bourtzwiller, France. This factory is located in the Alsace Lorraine portion of France which was traditionally German speaking, so it's in some respects the production of German PP series pistol by German speaking people who have been part of Germany off and on depending on the outcome of various wars. The Manuhrin pistols were made on the same slide and frame forgings, and tooling as the Zella Mehlis pistols, which Walther moved west ahead of the Soviet army in 1945. The fit and finish of these pistols is excellent, although they lack the collector appeal of the earlier pre-war ZM pistols, or the wartime nazi marked pistols. The good news is that this makes them the hands down bargains in the PP series pistols.
4. Beginning in about 1960, Walther started producing PP series pistols of its own in Ulm Germany. However, they imported fully finished and assembled PP and PPK frames and small parts, along with milled but unpolished, un-roll marked and un-heat treated slides. Walther then roll marked the Manuhrin milled slides, used an induction coil process to heat treat them, then polished and blued the slides, finished assembling them with Manuhrin parts and put them on the Manuhurin made and finished frames. These pistols were then proofed and inspected in Germany and given German proof marks. Given the differences in heat treating and bluing processes, the match between slides and frames is not always perfect, but these pistols, arguably no better than the Manhurin made pistols and mostly made by Manhurin, have Walther roll marks and German proof marks and seem to command more money. This arrangement continued until 1986.
5. In 1986 Walther finally started making its own complete pistols and the arrangement with Manhurin ceased. The bad news is that most folks agree the quality of these post 1985 Walther pistols is not as good as it was on the Manuhrin made or Manuhrin/Walther made pistols.
6. Interarms had been importing Manuhrin made PP and PPK/s pistols into the US, and with the cessation of the Walther arrangement with Manuhrin, production of PPK and PPK/S pistols was started by Ranger in Gadsen Alabama. The good news here is that as a US made pistol, the PPK no longer had to meet the import points criteria that led to the creation of the PPK/S. These pistols were again very nicely made and they continued in production until 1998, when Interarms closed it's doors.
7. In 1999, to fill the gap this created in the US market, Walther entered into an agreement with Smith and Wesson to produce the PPK and PPK/S in the US. These pistols are also well made, although they have been subject to a couple recalls and there were some QA issues mostly related to minor changes S&W made in the design. They lengthened the tang and made some slight dimensional changes in the grip frame and other places - just enough to make things like parts interchangeability and fitting of grips problematic. The long tang helps reduce slide bit for people with large hands, but it also makes the pistol less comfortable to carry in an IWB holster, and it detracts from the lines of the pistol.
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Overall, the Manuhrin and Range pistols were both very well made and I prefer them to the S&W versions, mostly because they don't incorporate the S&W design "improvements". But that said, a good S&W PPK or PPK/S is still a very nice pistol and I would not turn my nose up at one. On the other hand, you can get a minty Manuhrin made Interarms imported pistol, or an Interarms branded Ranger made pistol for less money than a new S&W and they are both, IMHO, better pistols than the new S&W version.
On the other hand, the S&W pistols may well be better than what, if anything, follows, so I would not pass on one of them if you're interested in a new PPK or PPK/S.