Fireman,
It is military brass. The "FA" in the head stamp stands for Frankford Arsenal (FA), Philadelphia, PA.
Frankford Arsenal was at one time a government owned, contractor operated plant that produced among other items, U.S. military small-arms ammunition.
According to the Weapons Research Division of Court Information Services Co., Inc., of Missoula, Montana: "FA 57 MATCH ammo was made by a new process that reduced the number of drawing steps from 4 to 2. A result was the casehead was unusually soft. The pressures of firing would cause the primer pocket to expand and make it difficult to reload safely. For this reason FA 57 MATCH cases should not be reloaded."
