The story of the .45ACP Lugers is a bit complex, and widely misunderstood. What most people believe is that two such guns were made for US military testing, one was lost, and the other is worth a million dollars. Well, that's virtually all incorrect. In actuality, probably about a half dozen were made in a couple different forms by DWM. That does include two for US trials, but neither of those guns is known to still exist. What is interesting is that it is actually pretty easy to know that. We have a photo of one of the original trials Lugers in the 1907 trial report, and when compared to the "million dollar Luger" (which actually went for just under $500,000 when it was last sold in 2010), it clearly has a slightly different grip angle. Fact is, the US insisted on a 60 degree grip angle instead of the standard 55.5 degrees for the Luger. The two trials guns were made with 60 degree grips, but the handful of other experimental and prototype .45ACP Lugers - including both of the ones currently known in the US - have the standard 55.5 degree grips. In addition, both of the ones in the US are chambered for standard .45ACP, where the trials guns used a 1906 version of the .45ACP cartridge which was a millimeter longer. The two guns in the US today are authentic DWM Lugers made by the factory in .45ACP, but they were made for purposes other than US military trials. There would have been potential for commercial sales, and other countries interested in a .45 version besides the US, and that was the reason those two guns (and probably a couple others since lost) were built.
http://www.forgottenweapons.com
