This is the Armscor M1911-A1 .22 WMR 14-round magazine.

Here is some more information about the Rock Island 1911 chambered in 22 WMR.

It’s the first in a carefully designed 1911 and packs the powerful 22 magnum cartridge with a 14-round capacity. Engineered with a pinned, solid state 5” barrel with delayed blow back slide and our crisp, factory 4- to 6-pound trigger to offer match class accuracy and power. Includes low profile anti-snag angle front and rear sight with skeletonized hammer and trigger with adjustable over travel stop. The XT Magnum is finished with rock-tough parkerized coating, fitted checkered rubber grips and comfort extended beaver tail safety.