The near-infinite variety of records in military pension files is the very essence of a truism: a statement that is obviously true and says nothing new or interesting. And yet, of course, you do not know what will be in any particular pension file until you look. It is in looking that interesting things are found. Egads, another truism.
A Civil War (or later) veteran’s answer to “Call Number 13” is one of those interesting things that will only be found in certain Union Civil War pension files. You can read about Call 13 and the circumstances under which it is found in “Did Your Civil War Ancestor Respond to Call Number 13?” NGS Magazine, Vol. 42, No. 2 (Apr.-May 2016): 35-39.