Small dusty box of some sort

 is a miscellaneous item in Fallout and Fallout 2.

Characteristics
A standard television dinner, consisting of a Thanksgiving meal of turkey, cornbread dressing, frozen peas and sweet potatoes. The contents are definitely not edible at this point and wastelanders are not sure if it ever was.

Fallout

 * Inside a desk in Junktown, in the building next to the Crash House.

Fallout 2

 * One in the fridge where the Slags live.
 * In the fridge under the Malamute Saloon.
 * On a bookshelf in the backroom of New Reno Arms.
 * In the lower right-most room on the second level of Vault 8

Behind the scenes

 * The sprite is actually a digitized image of the original TV Dinner created by C.A. Swanson & Sons.