Just to clarify a few things, or at least my attempt, based on what I've learned.
The war two version, from any of the three makers, is marked 'P. 38' with a period after the 'P'.
This does not hold for the commercial & military marked Model HP of course.
Most post war alloy frame guns that are marked 'P 38".
Note the
lack of a period after the 'P' on the slide.
The 'P 1' was the military designation of the P 38.
Same gun. It went through the same design changes noted below.
Fat slide.
This reinforcement change was instituted to address the issue of slides cracking from fatigue on the post-war made guns.
Here is a photo of a 1977 European commercial P 38 - (note lack of serial number on the frame) with the fat slide and reinforcement pin in the frame.
Notice the taller height of the slide opening on the left side. It is all the way up to the extractor. Also notice the grasping grooves on the slide go forward past the tip of the safety lever.
.
Compare these two features to that of the WWII gun photo from Post #25.
The WWII version and earlier post war slides did experience a
very small percentage of slides that cracked on the left side.
So the 'fat slide' is, in essence, a 'tall slide'. Who knows how the name started, because the slides are the same width. Go figure.
The hexagonal pin was a design change to extend the service life of the frames. Walther, at the request of the German army, did retro-fit some earlier frames with the hexagonal pin for testing before the adoption of it as standard for the military on new guns.
The pin never became standard on commercial post war guns, although the fat slide did.
I would have no problem making a post war P 38 without the pin and fat slide my regular shooter.
Same with a WWII version, after having changed the recoil springs for new ones.
I would not recommend the hammer drop on a WWII because it puts undue stress on the square cut firing pin and could break it.
Post war guns use a round pin that is not interchangeable.
To answer the grip 'broken line' question.
Walthers original blueprints for the WWII redesigned grips per the Army request shows 5 broken lines
around the grip screw.
For some reason the blueprints never made to the guys at both Walthers in - house grip department or to their prime grip contractor AEG.
They made the grips with six broken lines from start to wars end.
Mauser emulated Walther with the six line break with their bakelite grips and also the later plastic ones.
Spreewerk - no e on the end - in northern Czechoslovakia, however, paid attention to the original drawings.
Or at least their grip contractor, who was named Julius Posselt, did.
All Spreewerk P.38s, other than the early guns that used Walther made grips, have the correct five broken lines.
Jim, The brown bakelite grips are consistent with a mid to late war commercial.
Walther continued to make commercial marked - banner and address - P. 38s throughout the war. The degree of finish mirrored the military version as the war progressed.
They were for sale in Germany and most were targeted for sales to military Officers, as the general staff had to provide their own.
At least that is my understanding.
JT
