Mike,
1928 Navy is a good call, I think. Schwing's "Standard Catalog" calls these 1923 Commercial and Military, claiming that the first 1000, made by DWM (BKIW) were available in the Netherlands to both the Military and Commercial sales. He goes on to assert that the next 400 pistols, proofed with a c/c/U proof, were made by Mauser for Dutch Air Force delivery. He appears to have gotten his information straight from Kenyon, who at least took a look at the guns' characteristics and allowed as how they may be purely military guns.
Martens & De Vries (The Dutch Luger) more appropriately call them 1928 Navy, for the year that the Dutch Navy adopted the pistol and took their first delivery. According to August Weiss, 77 pistols were delivered in July 1 1928, 492 pistols in Feb. 1929, 515 pistols in July 1929, and 400 pieces in Jan. 1930. This puts your Luger in the second delivery. Serial numbers ran from 1 through 1484, and these pistols were proofed with the c/N commercial proof.
I don't know what to tell you about the "look" of the extractor, although GELADEN on both sides is proper, as you note. I don't know about the lack of grip numbers, but Martens & De Vries (p.145) show a Mauser-produced 1928 Dutch Navy (the next contract delivery, c/c/U proof) #1714 with exactly that profile grip-top cut under the side plate.
The serial numbers on the bottom of the barrel are curious, and I am curious to know if there is a c/U there.
For the sake of comparison, here is a link to one of these pistols for sale at Simpson, Ltd:
http://www.simpsonltd.com/product_in...oducts_id=2218 See if you think the finish of the extractor looks different from the rest of the breechblock.
--Dwight