Joe,
your group photograph is that of a typical group of k.k. Gendarmerie in the 1899 pattern blue uniform. The Imperial Decree of 5 July 1899 introduced a leather spiked helmet for the Austrian Gendarmerie replacing a feathered cap worn prior to this date. This in turn was replaced following the Decree of 25 May 1902 by the pattern in cork for security duties, the leather version still being used for parades.
Now, whereas the peacetime Gendarmerie were the k.k. Gendarmerie in the Austrian half of the Monarchy and the k.u. Gendarmerie in the Hungarian half, those Gendarmerie elements mobilised for service in the field became the k.u.k. Feldgendarmerie.
Regards
Glenn