I found a pic of an original Clamshell box and it looks like mine is not it. This box I have has the bottom insert like a clamshell but it does not have the little finger divots in the foam around the tools. Each tool relief on a clamshell box has two divots, one above the tool and one below the tool to make it easier to remove the tools for use. Also the top half would have had a matching styrafoam insert that fit the gun like the bottom half. This could be missing and replaced with the piece of foam that is now in the top half of my box but since the tool divots are not there I dont think it was a clamshell.

Inside of box with the material removed.