The Royal Arsenal at Amberg did not manufacture Lugers. During the period in which Amberg was manufacturing arms for the Imperial forces of Germany, only DWM and Erfurt made Lugers. Of those two, DWM was a private company contracted to make Lugers while Erfurt was, like Amberg, a Royal Arsenal. Erfurt also made rifles and machineguns. I'm not certain if Amberg made anything other than rifles except that they didn't make Lugers. There were also Royal Arsenals at Danzig in what's now Poland and in Spandau, a part of Greater Berlin. The few examples of Spandau-marked Lugers are considered by most collectors to be fakes.