It is a German 9cm C/1873. These were in both German Field Artillery and Foot Artillery service. The Ottoman Artillery also used these throughout the Russo-Turkish War, WW1 and into the Turkish Revolution.
I have one of this type that I have restored. There are only a hand full of these in the US. This is a link for the page on my 9cm C/73:
Well, a 21cm Mrs L/12 or 10cm K. 1904 would be nice…By the way, I got a shipment in today from Germany for the parts I needed to complete a 10,5cm lFH 1898/09 Limber.I have just updated my web site to include these.
Again—thanks for putting the information on this 9cm C/73 on Landships.I will have to visit this gun someday.