Sorry for nitpicking, but it's 奉公袋 hōkō-bukuro, not 慰問袋 imon-bukuro. The former means "public service bag". It was given to soldiers by the army, and soldiers put their valuables in it when joining the army. The latter means "comfort bag". It was sent to soldiers from civilians for the purpose of encouraging them, and it contained toiletries, dried fruits, canned foods, letters of encouragement and so on.