THE FIRST XXX ROUND BOX MAGAZINES
After the publishing of Thompson: The American Legend, another collector on the newsletter called me with the happy news that he had "discovered" one of the magazines described on page 198. He had bought the magazine years before as a shooter mag.
These magazines were produced for the Armored Force Boards testing which culminated in the report issued on December 6, 1941. The reason for the tests was to provide a more reliable means of supplying the Thompson with ammo, instead of the drum. The box magazines available only carried twenty rounds.
The early thirty round magazines were produced by taking two twenty round magazines and cutting the bottom off of one and the top two thirds of the other. Then welding the two pieces together. The welds are almost invisible. The magazines were further modified by having bullet count marks and windows cut into the side wall.
The twenty rounders were both Crosby production. The markings on the front face are what catches the eye first. The markings almost look like an accidental double strike.