Perhaps it was a cap sewn by mom or "the wife" for casual wear, sleeping, or those times when the soldier had to perform "Elf Duty." The soldier had his picture taken with it to send home to show that he had actually worn it and unfortunately for him that's the picture that survived the war. I remember a particular mint green suit my son's grandma sent for him to wear at Easter. He was very young and I didn't want him to suffer childhood trauma so we dressed him in it, I took a few snapshots to send to his grandma and he never wore it again.