DBU Kraft Stoff filler cap

[13starsinax]

Hello, long time reader. This Forum has provided me with hours of reading, and great help. I am an amateur collector of Luftwaffe history. Recently I transitioned from signatures on postal covers to aircraft artifacts. It is daunting at the beginning, but I am trying hard to expand my knowledge.
I read the hints to new members, and that is my introduction.
Now that I can post I hope to help others as well.


I recently purchased this item, and I am stumped. After hours of reading I can not re-find the information I am basing my thoughts on what this is. I remember seeing a diagram of a drop tank that had an access hatch, and the filler cap under it. So, I figured this would be a good beginning with you all.
-It only has one hole on the ears for the retention chain.
-No vents.
-A makers mark I do not recognize.*see edit


If you could please help me with a link to the information, and how you found it, that would be very helpful.
Thank you