The headstamp you describe is indeed one of many used by U.S. Cartridge Company (USCCo.) but I’m not sure what the dates of this specific one may be. There is a flat head and a dished one too. USCCo. headstamps were used to 1935, even though the last few years were under WRA ownership.
I doubt this was for military use as they didn’t use #1 Buck much, if any. Shotgun shells were rarely uniquely stamped, like metallic cartridges, for military use. Boxes were generally marked in someway but not individual shells, as far as I know. During WWII a lot of shotgun shells were purchased by the U.S. Government and they were standard production runs of shells with standard boxes, marked as government owned. Even though this box (pic) was made for a military contract late in WWII, note the shells are standard Winchester Ranger trap shells.
Value, like beauty, is in the eyes of the beholder. Look around at some of the online auction sites and you may get a comparison.