The 10cm Kanone m04 is one of the more anonymous guns in the arsenal of the Germany Army in WW1, but it still must be given status as one of its real work horses. When the war started in 1914 the German heavy artillery consisted only of four types (not counting the more exotic super-heavies, of course) and that was the 15cm Feldhaubitze, the 13cm Kanone, the 21cm Mörser and the 10cm Kanone m04. It was for a long time the main long range gun of the German Corps Artillery, and as such bore much of the important task of suppressing the enemys artillery and conducting harassing fire against critical road junctions, etc.
Despite its name, it had been accepted into service in 1905, and it was the second heavy gun with modern recoil system accepted by the German Army. (Its age shows in one telling detail: the absence of a shield.) One detail, very characteristic of this gun, and not continued in its successors, is the vertical sliding breach block. It weighed 2800kg when deployed, 3509kg in marching order.
The muzzle velocity was 551m/sec, and the maximum range was 10,200 meters. It could fire a number of different 10cm shells, including several different HE and Gas. It could also fire the special 10cm Granate 15 Haube (Hood) for extra range. The standard grenade used during much of the war was the 10cm Granate 15, weighing 15kg, and having an explosive charge of 1.8 kilos. A variant of the 10cm m04 was the 04/12 which differed little from it, except that it was equipped with a special shield. It was eventually superceded by a much modernized 10cm guns, the m14 and then the m17.
The 10cm Kanone m/04 below is on display in the remarkable Army Museum in Brussels. I have examined the paintwork and believe it to be original.
Below you can see the tube of the gun only, on display in the USA, and photographed by Mike Casale:
There is a detailed walkaround of a Kanone m.04 at the AMMS Brisbane website - this gun is at Nundah, Queensland. This gun was restored some years ago.
Thanks to Jack Mueller for corrections!