Although it does not answer you question, the Rangliste might add perspective.

I looked at Rangliste des aktiven Dienststandes der Königlich Preussischen Armee und des XIII (Königlich Württembergischen) Armeekorps nach dem Stande von 6 Oktober 1913. It can be found on Google, as linked below (the listing says 1901, yet it is the October 1913 edition).

On page 461 one can see the 2 Oberschlesisches Feldartillerie Regiment Nr 57.officers where Hauptmann Herold is listed.

Note: This is the active list; he is also so listed in the separate work for 1913 - I have a hard copies of both, but this one I can not find on Google. The 57th is on page 444 in that work and has Herold as well.

The Rangliste uses St for Staff (Stab),

Depending on the context, form and structure of your list, St might have this meaning.

Just some thoughts. - R.