Is this a trick question?
He has another '73 in his scabbard, just not as fancy.
Crescent shaped butt plates have been around for a long, long time.
The reason for crescent shaped buttstocks is that when used properly, they encirlcle the upper shoulder joint and the butt does not slip up or down.
The predecessors to the Winchester rifles, the Volcanic and Henry rifles, all had crescent shaped buttstocks. That was the only way they came.