Recently I have managed to acquire a variety of XM162 shotgun ammunition, ranging from the early Vietnam era to the 1980s.
This is an early 10 round box, manufactured by the Federal Cartridge Corporation.
This box is not dated. I have tentatively dated it based on the rounds it contained, which are the earliest style that I know of. I took a round out and photographed it before resealing the box.
The early ammunition was essentially just repackaged civilian ammunition.
The earliest cartridges had roll crimps rather than star crimps. It is my understanding that the change was made in the mid 1960s.
This next box was also manufactured by the Federal Cartridge Corporation. Though it is labeled XM162, it contains experimental XM257 shells. Later iterations of the XM257 shell were produced in subdued colors with darkened brass.
Later boxes were packaged wrapped in a foil package. The earliest I have seen was dated 1964. This example, manufactured by the Olin Mathieson Chemical Corporation, is dated 1967.
Federal continued to manufacture ammunition for the government throughout the conflict. This 10 round box is dated 1970.