The WIKI for "United States, Spanish American War Volunteers, 1899-1927" states:
"Key any ranks in the prefix field. If there are incoming and outgoing ranks, key the outgoing rank (2nd rank)."
What are "incoming and outgoing ranks"? Anyone who has ever been in the military can correctly imply that:
1 Lieutenant stands for the rank of "First Lieutenant";
2 Lieutenant stands for the rank of "Second Lieutenant";
1 Sergeant stands for the rank of "First Sergeant"; and
Q M Sergeant stands for the rank of "Quartermaster Sergeant", etc.
This is just another pitch for following the rule: "Key it as you see it"!
Please don't try to rewrite history!