"Karth" Marking on German 10cm Kanone 04 Case

Does anyone know the meaning of the marking “Karth” in calligraphy style writing at 12 O’Clock on the headstamp of a German 110x505R Kanone 04 case?

The primer also has some unusual markings "Schlgzdschr14 (definitely no vowels in that word), and “ELSb” in calligraphy style writing. It is a 16mm 3 slot screw-in type.

Any info on these markings would be helpful.

“Karth” means "Kartuschh

Sorry, it is “FLSb”, not “ELSb”, and is followed by “RB” in a circle.

Here is a drawing I did of the markings in MS paint:

Falcon, this is the manufacturer and will be “Feuerwerkslaboratorium Siegburg” (military facility).

Thanks for the info EOD, what do the letters “RB” stand for? There are also the faint remains of an ink stamping on the base (not bad considering it’s been there 93 years), which is the letters “AP” in a square, what does this mean?

Falcon, I wish I would know.