Hello!
I think, Grey C is wrong.
According to the Oldenburg medals, Major v. Bartenwerffer of the Generalstab didn´t have any Oldenburg medals.
I´ve found the right one in the 1908 ranklist in Generalstab V.Armeekorps Posen.
He promoted to Hauptmann 20.3.06 and in 1909 he served with 5th comp./Leibgarde-Inf.Rgt,.115 (Hessen)
He had this Oldenburg medal:
OV3b: http://www.ehrenzeichen-orden.de/deutsche-staaten/oldenburger-haus-und-verdienstorden-ritterkreuz-2-klasse-mit-krone-1860.html
Ranklist 1912: Chief of staff (3.Division Stettin), additional medal: RAO4, Hauptmann
Ranklist 1913: Chief of staff (3.Division Stettin), Major (prom.1.10.12)
Ranklist 1914: Generalstab der Armee, Großer Generalstab, Major