It doesn't seem to be from an aircraft. I didn't find the Fl number for the Luftwaffe stuff. Judging by the inscriptions it imay be a part of a fire device. An extinguisher would be possible. The "Abnahme" line is the data of the device acceptation So, it was accepted in 1941. The BAl number is a inspection stamp. Possible pressed by the factory.
A minor correction ... the weight data you posted should be
Empty ( Leer ) 12,5 kg
Full ( Voll ) 18,5 kg
Just there is the comma sign after 12 and 18.