Part of the standard issue US Molle II system: ubiquitous FLC. Aka, the fighting load carrier.
These are in ACU/UCP (that grey digital camo that blends in with a gravel pit and grandma's couch)
These have a single zipper on the front, but also have a waist belt and buckle that can be used in conjunction or standalone. Additionally, they can be reconfigured with the buckle in the back, and worn similar to a chest rig. Plenty of molle loops and can be adjusted to fit most anyone. There are also internal mesh pockets for soft goods or documents.
These will be from a variety of makers, but all are genuine US Government issue and in excellent shape.