cook to my grandparents who lived in michigan and their name is r.l. sensabaugh. >> her grandparents move to michigan after 1964. her father joined the namy in 1945. around the same age as the person who wrote the letter, sergeant cook. she thinks it was a family friend. >> i remember him but i don't remember anything about limb. >> reporter: was only 9 years old. >> and she opens it with a twist. >> there is nothing in it. >> the envelope was post marked from minneapolis in 2013. that is how it got back in the system. it is a letter from a man named patrick. >> hello there, i found this air mail envelope which had been mailed from an army sergeant, june 29th, 1949. apparently a couple lived in