About the Manufacturer:
Arcadia Machine & Tool, or AMT, was a firearms manufacturer from Irwindale, California that produced a line of pistols using the name AutoMag from 1982 to 1995. These semi-automatic pistols carried a name similar to the sole pistol model that the defunct Auto-Mag Coproration had previously produced. But, there is no connection other than the name similarity.
AMT did not fare well in business and eventually went bankrupt. AMT's assets and trademark were sold off and they passed between a couple of different companies until they were finally acquired by the High Standard Manufacturing Company of Houston, Texas. High Standard still produces various models under the AMT brand, based on original AMT designs.
About the Cartridge:
This cartridge was introduced along with the Luger semi-automatic pistol. The pistol and cartridge was first adopted by the German Navy in 1904 and then by the German Army in 1908. This cartridge has since been adopted by the military of practically every non-Communist power. It has become the most popular and widely-used handgun cartridge in the world. Performance wise, the 9mm cartridge has somewhat more power than the .38 Special but falls well short of the .357 Magnum.