I suspect that the “D W M” headstamp on 6.35 mm is from Karlsruhe, while the “D W M B” I know is from Berlin-Borsigwalde. I don’t have documentation for this, but the two headstmaps seem somewhat contemporary, and it would be an easy way to differentiate the producing facilities.
On the 9 x 25 mm Mauser Cartridge, the “Y A” stands for “Ypourgion Asfalias.” This is transliterated from the Greek alphabet, but the two initials remain constant. It stands for Ministry of Security. I am proud to say that with the help of Dimi Goulas, in Switzerland, I am the one that pursued this formerly unknown marking, sensing that it was a Greek contract. Dimi pursued it with a police museum in Greece on a visit there, and found I was correct. He even found a SMG, the Steyr MP34(ö), with these initials on the butt in the Police Museum. The ammunition was specifically for the mechanized police force, created in 1936 and existing until the German occupation in 1940/41. They used the Austrian Steyr SMG in this caliber, and I have seen a picture of them training with it. These cartridges were made in 1938 and 1939. It is obvious that with the German’s knowing they were going to invade Greece, that they cut off the contract, becuase The Greek Powder and Cartridge Company made some of this caliber ammunition in 1940 and 1941 with the same initials on the headstamp. The mechanized police, by the way, were a National Police Agency that made heavy use of motorcycles with side-cars.
I suspect the “Y A” cartridges by DWM were made at Karlsruhe, but I am not sure of that. The only 9 x 25 mm Mauser ammo I know of absolutely made by the Berlin-Borsigwalde Plant is a rare, lacquered-steel-case
version that was probably experimental, since the full headstamp is simply “B DWM B” without any entry at all at the 6 o’clock position on the cartridge head.
Regarding dating of Berlin-Borsigwalde pistol cartridges, the characteristics of most of them are from the mid to late 1930s. Again, though, I have no exact time frame. Of course, I am not including here the German military coded-headstamp cartridges, which are dated.
Reference: “The 9 x 25 mm Mauser Export Cartridge,” Wooding Laboratory, compiled by John L. Moss, appearing in IAA Journal Issue 424, Mar/Apr 2002, pages 6 - 20