Following the Korean War, the U.S. Military figured out that a lot of its gear was... archaic. On top of multiple belts and a weird hanger hook system that made things dangly, it wasn't customizable by the individual man. It was largely ok, but it needed an upgrade for the times.
Enter: the M56 gear. Then in about 1961, we discovered we'd made a set of gear that was a little iffy. So we tweaked it.
This is the "Case, Small Arms" for that gear which is a long way to say "pouch". At the time, the U.S. Military had two main Rifles in service, so it was key to have a pouch that could handle both types of ammo.
The idea behind the Small Arms Case was that it could handle two magazines for the M14 Rifle or two bandoleers for the M1 Rifle. Or even grenades! It comes with two loops that can carry grenades, which you hilariously aren't supposed to use as such.
The little hook on top connects to our suspenders to keep the pouch upright and also serves to add more points of contact to the belt for your suspenders. Doing so balances the load better.
This was used clear through the Vietnam War, and the odd M56 pouch shows up in photos of the invasion of Iraq when we were using everything we could.
This pouch will hold 2 metal 7.62NATO Magazines each. Or it will also fit 2 or 3 20 round M16 Magazines, but you may want to put a sock in the bottom to grab the shorter magazines better.
The first pattern pouch had a weird stiffener and an eyelet in the pull tab. The second pattern ditched those as unneccesary.