About the Handgun:
The Mauser M2 is a Mauser branded handgun which was offered in the United States by Sig Sauer. It is a self-loading double-action pistol offered in .45 ACP initially, and later in .40 S&W and .357 SIG. The Mauser M2 is dimensionally similar to the SIG P229 pistol, also manufactured by Sig Sauer. Unlike most SIGs, it utilizes a rotating barrel like a Beretta. It's also striker-fired, like a Glock pistol.
SIG purchased the Mauser name for pistol manufacture in 1999, but this pistol is no longer supported by SIG nor Mauser Jagdwaffen GmbH. It hasn't been imported by SIG since 2004, and the Mauser Oberndorf plant where the M2 was manufactured has been closed.
About the Manufacturer:
Mauser was a German arms manufacturer, maker of a line of bolt-action rifles and pistols from the 1870s on through the 20th century. Their designs were initially built for the German armed forces but have been exported and licensed to a number of countries through the years, as well as being popular civilian firearms. In the late twentieth century, Mauser continued to make primarily sporting and hunting rifles.
SIG (San Swiss Arms AG), acquired part of Mauser in 1999. This civil arms division was split off from the Mauser group, forming Mauser Jagdwaffen GmbH, which roughly translates to Mauser Hunting Rifles Ltd.. SIG recently made a Mauser branded M2 Pistol in 2000.
About the Cartridge:
This cartridge was developed by John Browning and was adopted by the United States Ordnance Department along with the Colt-Browning automatic pistol in 1911. It has also been made the official military handgun chambering by several other governments, notably Argentina, Mexico and Norway. The 45 Automatic is the most powerful military handgun cartridge in use today. This is a heavy and powerful sub-sonic round. Although its muzzle energy can exceed 400 ft-lbs, its velocity and bullet weight creates a steep trajectory curve that limits its effective range to self-defense distances.