The .25 Remington was indeed known in Germany as the 6.5x52, DWM case number 519A, though not as popular as the 6.5x52R aka .25-35 Winchester, DWM#519. Recently I was given several 25 Remington cartridges found in a drawer in an old hunter's household, resting there since pre-WW2. I have seen a Mauser K action rifle by Otto Bock, Berlin so chambered and also two Haenel 1909s. In their 1909 catalog Haenel called it the "Winchester 25/35 rimless".