The San Cristobal armory was a surprisingly large-scale arms manufacturer set up in the Dominican Republic in the late 40s. They produced several different weapons, but the most common was the Model 2 Cristobal carbine. Designed by Pál Király, it was a lever-delayed blowback mechanism chambered for the US .30 carbine cartridge (7.62x33mm).

When the bolt begins to move rearward, the lower short arm of the inertia-lever leans against the stationary shoulder of the breech-encasing. The rearward movement of the bolt causes thus rearward rotation of the inertia-lever, the upper long arm of which pushes violently rearward the heavy striker. the inertia of this latter makes itself in a degree , increased according to the lever age of the two arms of the inertia-lever. By this arrangement , thetravel from an electronic device at one end of the wire to the earphone or earphones, and/or a microphone at the other end of the wire. The wire, or wires, is preferably permanently sewn into the seams of the garment. The earphone may be retractable and/or kept in a small pocket near the collar of the garment to limit the movement of the earphone when it is not being actively used. The integrated earphone and microphone are preferably machine washable and dryable along with the garment with which they are integrated.”        
The Kochling Design Patent discloses the shape or ornamental features of the device which is disclosed in the published application to Kochling 2012/0060260.
The Tao Chinese Patent discloses:   