I've seen these referred to as Schnapper mounts. You compress the front 2 legs to remove it, the rear mount arm fits into a stud on the rifle. To effect windage you need to drift the dovetail the front mount clips onto. Now here's the next problem, finding or making a suitable base for the front mount. I've only seen these on Steyr made rifles so I suppose they're the original factory mount for Mannlichers.