After reviewing my questions upon starting this thread and conversation, I think that they have all but one been answered, and appreciate most of the input. To summarize my theories:
1. The watch was made leading up to, or during, WWI. Serial number can confirm precise date of manufacture.
2. The specimen was not a standard issue model, but rather conformed to the criteria that various military contracts established consistently to provide, for example, 12 and 24 hour time with seconds on a centered subdial. Trench Watch Guy's kindly-shared Omega design suggests that there was some variation in these contractual requirements, as demonstrated by the skeletonized hands on his example. Some contracts, as perhaps with my specimen, may have had a provision for a radio-luminescent feature in hour and minute hands or other specifications. The WWII and NSDAP elements of the question thus become moot points.
3. The movement is an officer's model 15-jewel known as the Rebberg movement, which is a designation not of the manufacturer, Aegler, but rather of the area in which it operated. This is an important and very significant transitional movement in the fields both of horology and the Rolex marque that is explored in detail and with excellent connection to Rolex and Hans Wilsdorf by David Boettcher at
https://www.vintagewatchstraps.com/aegler.php
4. This question remains unanswered; any input here would be appreciated. Various designs of shrapnel protective guards can be found in grill forms, spiral forms (Zodiac), field improvised forms, as well as that of this specimen.
5. Reductio ad absurdum.
6. Reductio ad absurdum.
Thanks for help in getting to the bottom of my inquiries in this thread. Any information on the shrapnel guard topic would be very much welcomed.
Best regards,
Prospector