That holster is one of the infamous clamshells that came out around mid-century. The hinge was spring loaded so that the holster would snap open at the press of a button for a lightning fast draw, and the swivel was so that the officer could tip the muzzle up and out of the way when getting into vehicles. Stories circulated that kids were sneaking up behind officers and pressing the button to watch the weapon fall out, but a more likely scenario was that officers were accidentally pressing the buttons themselves. In any event, a collector might pay good money for yours.