"Uncanny contrivances and thousands of keen-eyed inspectors armed with gages and micrometers ride herd on the millions of tumbling embryo cartridges for machine gun and rifle as they rattle with deafening clamor from one powerful machine to another at the government-owned Ordnance Plant here, operated by the U.S. Cartridge Company. Cartridges appear to consist of only four simple pieces: the bullet, the case, the powder and the primer, but their mass manufacture in astronomical quantities requires the same highly exacting standard employed in the making of a fine watch. This photo shows a unique inspection machine at the Local Ordnance Plant--one of more than 20 such plants throughout the United States. Just as a dentist puts a mirror in a patient's mouth to examine it, so does this case inspection machine hold a mirror to mouths of cartridge cases as they roll off the assembly line. By looking into the mirror, the inspector can tell whether the inside of the cartridge cases is perfect and that no foreign matter has lodged inside."