Need help to ID a WW1 German Casing

[Greatwar15]

I recently got a WW1 shell casing, and am having a tough time identifying it. I have just about all the common shell cases out there, but this one has me scratching my head. It is 159 mm ( 6 1/4") tall and has a rimmed base which is 132 mm (5 3/8") wide, the opening is roughly about 127 mm wide (inside dimension). It is not perfectly round, so hard to get a good measurement. So I am hoping to get some expertise on this item, thank you in advance.

It does have the following markings on the bottom, in case they don't show up in the pictures. Patronenfabrik X Karlsruhe 1915, also has a and "10" below the karlsruhe stamp.

 

[Michel]

It is a Kaiserliche Marine shell case made in oktober (X) 1915. It is not common but they turn up sometimes. My best guess is they are meant for the "beute" Russian 12,2cm M1910 howitser. There where 2 Marinekorps Schwere 12 cm Haubitze batterien active on the Western front named Kreide and Radler.

 

[Greatwar15]

I had also considered it would be for the 122 mm howitzer M1909 as well. But thanks for the info.