Roy and Mary Chapman of Homewood, Alabama: my father's parents. They appear to have some kind of a World War II booster sign on the front door and are posing with it. "We have a son overseas" or "We support War Bonds." It must have been something like that.
By August 1942, my grandparents in Alabama were concerned that they had not seen their son for seven months, mail service had only just begun to work with some regularity, and they still didn't know where he was. When Lt. Chapman was asked to stay on at his secret location--Ascension Island--it appears that he asked the unit's chaplain to write his parents and assure them they shouldn't worry.
Office of the Chaplain
38th Engineers
APO #1257, C/O Postmaster
Miami, Florida
August 3, 1942
"Dear Mr. and Mrs. Chapman,
I am the Chaplain of the organization to which your son, Lt. Chapman, is assigned, and take pleasure in writing this letter. He seems to be in the best of health and is quite cheerful in the performance of his duties. He is one of Uncle Sam's reliable officers and is to be commended for his worthy service. It has been a pleasure to know your son during the past few months.