Beginning in the late 1920's - the patent or display box
Per Standard Catalog of Smith and Wesson 4th Edition, page 52-53:
"Around the end of the 1920's, S&W introduced a new type of hinged box with the hinge attached to the bottom edge of lower portion of the box rather than the top edge. The front edge of the box itself was beveled to allow the box lid to close flush, and the box could be opened displaying the contents and thus the name "Display" Because the S&W's patent for this design is marked inside these boxes, they are sometimes alternatively known as "Patent" boxes."
So there you have it! Happen to also have its original contents?