I have been doing research on an Alexander Moore (or Alexander Moor) who died shortly after the attack on Fort Stevens in July of 1864. He was in Company A of the 61st Regiment Pennsylvania Volunteers. The Mariners' Museum Library, where I am an archivist, has a letter from him to his brother James C. Moore. I am wondering, Don, if this isn't your relative.
I do not have any information on Alexander other than the circumstances of his death. If you know anything about him, please do post. Thank you!