specifically, this edit: https://www.wikitree.com/index.php?title=Beattie-1229&diff=68707426&oldid=68706677
I don't see a source "S-1209", but there is a source "S-1809". Is that what you are asking about? Source "S-1809" is a source contained in the GEDCOM upload. Specifically it is "Pioneer Families of Washington County, Virginia". I had to look on his wife's profile to find this information. I don't think William is shown in that source, and maybe why it was unidentified. "S-1809" should probably be removed from William's profile.