As from October 11, 1939, Pelikan fountain pens were fitted with chromium/nickel (CN) - steel nib, as the use of palladium nibs for the domestic market was forbidden by the government⁽²⁾. It is likely that early CN nibs were lightly gold-plated (Fig.4 third from left). Some nibs had the half round slit for flexibility (Fig.1,4). please refer to Pelikan 100 (ca.1940) for further information on CN nib.

Until 1940, the body was made of ebonite section (Fig.6 left) and celluloid/cellulose acetate barrel (ver.1)⁽¹⁾.

In early 1940's, Günter Wagner introduced new material, acrylic resin to the barrels (Pelikan Schreibgeräte). With the introduction of acrylic resin, model 100N went into the "3rd generation". It seems that the material of the filling system was also (gradually) replaced with cellulose acetate. According to @stoen's observation, at first, Günter Wagner manufactured injection molded acrylic resin barrel with cellulose acetate stepped section (ver.2a)(Fig.6 right). Ver.2a section had narrower threading and could fit model 100 barrel, but the step would be too wide and collar / feed slot is of wrong type for model 100. Ver.2a bodies accept only black synthetic plastic seal (Fig.5 middle), because the “pork-pie-hat” piston nut of the cork seal cannot fit the back end of the section bore (Fig.7 bottom). Around the same time, the company manufactured injection molded acrylic resin barrel with cellulose acetate stepless section (ver.2b) (Pelikan 100N (ca.1940)). Ver.2b is compatible with ver.1, meaning that the section and barrel of ver.2b can fit the barrel and ebonite section of ver.1, respectively. Ver.2b bodies accept either cork or black elastomer seal. @stoen's observation suggests that the black elastomer seal was introduced to the model 100N sometime between 1940 and 1942, and coexisted with cork seal for a while. The reinforcing ring was no more installed on ver.2a and ver.2b. According to @stoen, both, ver.2a and ver.2b are rather uncommon, but not prototype, and were likely transitional model to ver.3.

Around 1942, Günter Wagner engineered the injection molded one piece acrylic resin body with step (ver.3). The grip section and the threaded portion were painted black on the inside. In the same period, the company gradually replaced celluloid with cellulose acetate for other parts such as cap unit, filling system, and sleeve (@stoen). In October, 1942, the black elastomer seal finally replaced cork seal (Pelikan Schreibgeräte). The advantages of one piece injection molded acrylic resin bodies (at the cost of serviceability) is probably productivity, cost, and quality control. @stoen found ver.3 pens had slightly wider grip/cap threading and ink window than ver.4, as ver.4 caps that @stoen has tried couldn’t fit the ver.3 bodies. @stoen also found that in “stepped” bodies (no matter, one or two piece), the section wall were rather thin, and would easily crack there. Thereafter, ver.3 body had been unchanged until after WWII.

Around 1949, the body was replaced with injection molded one piece acrylic resin body without step (ver.4). In ver.4, “design weakness” as seen in the stepped sections was improved, and fewer ver.4 pens developed cracks in that part.

Based on @stoen’s original research, I summarized the transition of the body of model 100N, showing its "evolution"⁽¹⁾.
 
Ver.1; Ebonite stepped section / celluloid or cellulose acetate barrel (1937-1940) (cork seal)

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Ver.2a; Cellulose acetate stepped section / injection molded acrylic resin barrel (1940-1942) (black elastomer seal (modified type))
Ver.2b; Cellulose acetate stepless section / injection molded acrylic resin barrel (1940-1942) (cork seal or black elastomer seal (modified type))

↓

Ver.3; One piece stepped acrylic resin body (1942-1949) (black elastomer seal (modified type))

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Ver.4; One piece stepless acrylic resin body (1949-1954) (black elastomer seal (modified type) → white synthetic plastic seal)

My pen with all signs of model 100N with ver.3 body of the 3rd generation, may be dated ca.1942. 

Note;⁽¹⁾To tell the truth, I didn't notice that evolution, until pointed out by @stoen. As you know, "version" is just for a descriptive purpose. Whether there was a body evolution in model 100 remains to be elucidated.
²⁾Some export market pens had gold nibs (1940 Gray Pelikan 100N Set).