The AMT Backup is a small semi-automatic pistol. It was first manufactured by the Ordnance Manufacturing Corporation (OMC) of El Monte, CA. The first guns made in .380 ACP by OMC are known as the OMC Backup. OMC produced a short run of these pistols before the tooling was purchased by Arcadia Machine & Tool, who took over production. AMT .380 ACP Backup pistols were made by AMT in El Monte, Covina California, and Irwindale, CA. The AMT Backup was available in a wide range of calibers: .22 LR, .380 ACP, .38 Super, 9×19mm, .357 SIG, .40 S&W, .400 Corbon and .45 ACP have all been offered.