(Official nomenclature acquired)
This kind of cartridge belt pockets came with M-1918A2 BAR rifle in the Vietnam War era. Just like M-1937 BAR Cartridge Belt, each sector has three pockets.
The main body of the pocket is made of cotton duck canvas, and the magazines are secured by a nylon strap with snap. The nylon straps are also used as belt rings on the back. Each sector has two sets of M-1910 double hook eyelets on the bottom rim. They are supplied with standard M-1956 Pistol Belt and Suspenders.
We got two versions: one with LTD snap buttons and the other with normal round snap buttons, the round snap button one is slightly shorter.
We personally infer that these cartridge pockets were produced specifically for the military aid M-1918A2 BAR rifle due to the depletion of M-1937 BAR Cartridge Belt stock.
It appears in the famous documentary Tales of the Gun -US Guns of WW II