I add some lines about the 7,5 cm.
A 7,5 cm L/35 Krupp Räderlafette is mentioned, in use around 1910, at the Kaisermanövern.
There is also some info about the 7,5 cm L/60, the germans having a "restbeständ" when war break out. It was produced in Germany also, and sold to other countries, especially Spain during the civil war. The germans made use of it(eingestellt) in 1932.
Other 7,5 cm Flak mentioned and used by the germans, is the Norwegian 7,5 cm Flak M32, the french 7,5 cm Flak M17/34, M36, and M33.
Info from "Flak" by Horst.A.Koch, and "Deutsche Flug-Abwehr im 20.jahrhundert by Otto W.von Renz.
The 7,5 cm Flak was used a lot in Norway, 7,5 cm Flak L/60(Krupp), the the norwegian 7,5 cm Flak L/45 MK32, 7,5 cm L.V.K. L/45 M/16 (n). Adm. Polarküste had in autumn 1941 listed 12 X 7,5 cm Flak 28 (beute) around Narvik (mfl.abt.706), and 32 X 7,5 cm Flak in use in Narvik area in autumn 1942.
The 7,5 cm Flak(Türk) is also on lists over flak in Norway, Narvik area if im not wrong.