Some brief history on Walther PP series pistol manufacture.
1) Walter started making the PP in 1929 and the PPK in 1931. No military acceptance stamp or waffen eagle was used from 1933 to 1939.
2) The Walther plant at Zella-Mellis was over run by the Soviets and remained in the Soviet zone of occupation. Walther escaped to the West with what ever it could, and the remainder was captured by the Soviets. A majority of that tooling was moved to Russia, where it went largely unused, however some of it was moved to Suhl, where there was some post war East German production of PP's from armoury kits and spares found in the original factory, plus newly made parts.
3) After the war, West Germany was prohibited from small arms manufacture under all but very limited and tightly controlled circumstances. Beginning in 1952 Walther contracted with Manufacture de Machines du Haut-Rhin (Manurhin), in Haut-Rhin, France to manufacture the PP and PPK. Under this agreement the forgings for the slides and frames were made in Ulm Germany, then shipped to Manurhin where they were milled, polished heat treated, blued and hen assembled using small parts made by Manurhin. The only Walther contribution was the forgings.
Haut-Rhin is in the Alsace region of France on the west bank of the upper Rhine and if you know your post-WWI history you knew it was German territory up to the end of WWI. Thus, the post war PP and PPKs were being made by French Germans rather than German Germans.
The post war Manurhin made PPs and PPKs were initially imported into the US from 1953 by Tholson Co. and from 1956 by Interarms. These firearms are marked on the right side of the slide with the Manurhin roll marked and Walther license information and roll marked on the left side with the importer's roll mark.
4) Once the restrictions on West German small arms production were lifted, production of the P-38 was moved back to the new Walther plant at Ulm after a few years, but PP and PPK production remained in Haut-Rin with Manurhin.
Walther once again started "making" PP and PPK pistols, however, the only difference between these "Walther" made pistols and the Manurhin made pistols is that Maunurhin shipped finished frames and small parts a long with not yet heat treated, roll marked, or blued slides to Walther in Ulm Germany. Walther then induction heat treated the slides, roll marked and blued them and assembled the pistol using the Manurhin finished frames and small parts. These pistols often have frames and slides where the bluing doesn't quite match.
These PP and PPK series pistols are considered to be "Walther" and "German" made because they were proof marked in Ulm Germany by Walther. The Manuhrin marked guns imported to the US were in the EXACT same box as Walther guns, and had the EXACT same manual (the pictures of Walther marked guns, had the Walther markings airbrushed off, and Manuhrin markings added). The guns are one and the same.
The PPK/S was a development of the PP and PPK using the short PPK slide on the PP frame in order to create a semi-auto pistol that was large enough to meet the import restrictions of the Gun Control Act of 1968.
In 1984, Manurhin started importing new pistols directly and they were marked Manurhin on the left side of the slide. In 1986 Walther discontinued it's arrangement with Walther and started making complete PP and PPK pistols. I can recall magazine ads during this period where both claimed to be the makers of "original" PP series pistols. For what it's worth Manuhrin made better pistols than the post 1986 all Walther made pistols, but Manurhin stopped production in 1986.
5) GCA 1968 meant the smaller PPK could not be legally imported, so Interarms was interested in developed licensed US production of PP series pistols. As a result of this, Interarms obtained a license to produce them in the US and contracted with Ranger Manufacturing in Gadsen Alabama which began production in 1979 with the pistols bearing Interams roll marks and distributed by Interarms.
Ranger made the PPK and PPK/S, and made the PPK/S in both blued and stainless steel and chambered in .380 ACP. They also produced pistols chambered in .32 ACP, but only from 1997 to 1999, so they are uncommon.
These were fully licensed Walther pistols and stayed true to the Walther drawings. These are very well made PP series pistols and the stainless steel version is a plus for a carry gun. This license agreement was discontinued in 1999 when Interarms closed it's doors.
6) Starting in 2002, Smith & Wesson started making a licensed version of the PPK and PPK/S in Houlton, ME and continued to make them until 2017. Unfortunately, S&W felt a need to make a number of changes. For example, they changed the grip frame with the result that most PP series grips won't fit, they lengthened the tang, which eliminated hammer bite for a few people, but made the pistol uncomfortable to carry in an IWB holster, and they changes the safety lever to a design that resulted in ADs and prompted a recall in 2009.
In my personal experience I had more reliability issues with the S&W PPK/S than I ever did with any of my Ranger made PPK/S pistols or my Manurhin made PP pistols.
7) In 2017 Walther Arms began producing the PPK and PPK/S at their new US manufacturing plant in Fort Smith, Arkansas. I have not encountered on of these in the wild, but my hope is that they reverted to the original design and deleted the S&W changes.
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Price wise:
A) the pre-war Walthers are where the collector interest lies and price depends on condition and the details of what it is, when it was made and how it's marked.
B) Despite being, objectively speaking, lower quality than the Manurhin marked pistols, the post war Walther pistols generally bring a bit more money ($100 or so) in the same condition. Snob appeal I guess. The Manurhin pistols will bring around $600 in excellent condition, with the less common pistols, such as a PP in .380 ACP rather than .32 ACP bringing another $100 or so.
C) The Ranger made pistols fall in the same category as the Manurhin made pistols and will probably bring a bit less than a post war Walther in the same condition. They'll bring $600 in excellent condition with box. The uncommon .32 ACP pistols will being $200-300 more however in excellent condition.
D) The S&W Walthers have their fans, but they are low man on the totem pole when it comes to rank ordering Walther pistols by maker. S&W should have left it alone rather than trying to make changes. Still in excellent condition you'll get $400-$500 for one.