ONE CARTRIDGE, NOT A BOX! The box is for reference only!

One Cartridge not a Box,  28 Gauge Shotgun shell, by Herters USA, New, Modern, Black Plastic Case, Number 7½ steel shot with "* USA * 28 GA" Head-Stamp. See picture for priniting on black plastic case.

A short story on shot-shells:
Shot-Shells have been produced for over 2 centuries in many sizes, from 00 gauge to .360 gauge  and also in millimeters sizes.
For those not familiar with shot-shells the lower the gauge number the larger the size. A 20 gauge is smaller then a 16 gauge, a 16 gauge is smaller then a 12 gauge etc.
A gauge is a unit of measurement in shotguns, determined by the number of lead balls the size of the gun's bore (inside barrel diameter) that can be produced out of a pound of lead.  A 20 gauge gun size has 20 balls per pound, a 12 gauge has 12 balls, hence the smaller the gauge number the large the bore or size of the shell