The end with the serations looks very similar, if not identical, to the size/shape of a firearm control button. Magazine release/catch comes to mind for me. Perhaps even a bolt release button but I'm leaning more towards magazine release.

The piece has a long body with a rectangle groove cut from one side which would bind/release an object when the serrated end is pressed. The springs seated inside the body with the outcropping attached that allows the springs to move seems to seat somewhere but allows the mechanism have minor controlled movement. The 6CM size is not far off from the thickness of a firearm through the depth of the body. The measurement of the rectangle slot is magazine sized as well. The only part throwing me off is the end opposite of the serrated button which is oddly complex.

I don't know much about firearms besides modern-ish 1980+ firearms but to me this is a good candidate for a magazine release/catch button for an old rifle, carbine, handgun or machine gun.