As it turns out, I made a bone-headed mistake–the confirmation document was for his father not his grandfather. As soon as my neighbor saw it, he knew it had to be his father because he remembered the day and month of his birth but not the year. They matched and the history book confirmed the year. The old document has made it home after all these years. It did my heart good to leave it with him. He plans to show it to his brothers yet this week.
During my visit we looked over old photos and had a nice visit overall. (contented sigh)
As for how this item got to the antique mall, it would be a fascinating story but, alas, one we will never know.