This is a factory Ruger Security-380 .380 ACP 10-round magazine.

More information on the Ruger Security-380 pistol:

The Ruger Security-380 pistol is constructed with a hard-wearing anodized aluminum chassis and full-length guide rails. The grip frame is made from glass-filled nylon with a similar texture and feel to Ruger’s Security-9. It is the same size as the smaller Security-9 but much lighter, weighing 19.7 ozs when unloaded. It uses the same Secure Action trigger system of the Security-9, which has an integrated safety, neutrally balanced sear, and hammer catch. A single-sided manual thumb safety, push-button magazine release, and slide-stop lever on the left side of the frame are also included. The magazine holds 10 rounds and an extended 15-round magazine with a textured baseplate to extend the grip is also available.