I have been trying to identify this cylinder that I found on a walk. What could it's purpose be?
The cylinder must remain unharmed
It is imperative.
Please do not bully the cylinder.
Given the originally red colour, the slender shape and the mounting, it was probably a gas bottle for acetylene. The valve is missing. The text mentions "Duisburg", probably the location of the manufacturer.
EDIT: Acetylene bottles have thead for a protective cap. So my next guess is a fire extinguisher.
What sound does it make if you hit it with a stick?
We rapped on the side and it felt very solid, we didn't think to whack it with a stick.
I would say that a sledgehammer would be the right tool here.
I can't read rusty foreign text very well, but if I had to guess, it probably loosely translates to something like..
'DON'T FUCK WITH ME, BOOM BOOM'
Let us help you identify that mysterious object you’ve found.
Currently in CHALLENGE mode: If you've got something obscure knocking about, post a picture, and let's see how we do. Please prefix such posts with "CHALLENGE:" so we know we've got a fighting chance.