WWII German original steel tank used for either oil or gas.  Based on size, I say it's a Gas tank.  Tag on side says 20 liters.  Heavy steel, very strong it's been partially restored. The outside has been stripped and painted in the proper flat Green/Gray.  This tank has a outlet in the middle bottom, threaded and on top it has an offset fill that uses the same gas cap as a kubelwagen!  Same exact cap and chain.  Next to the cap is a threaded inlet.  

Original German WWII issue, but exactly for what I do not know, having restored many German WWII vehicles, still not sure.  But it can be used for anything!  A small tank, halftrack, truck or anything!  No rust, no holes.  Inside is covered in oil and will need to be washed out before using to keep it clean inside.    Weighs 19 pounds boxed so heavy to ship.

Measures 19 inches long, by 8.5 inches wide and 8.5 inches tall.