Mystery Access Panel

Feeling in needs of something hands-on, I extracted the illustrated panel from the junk in my garage.

My memory of where it came from is a bit hazy, but I suspect it came from a wooden crate purchased (by someone else) from 25 MU containing a job lot of unseen items. Selling off unwanted crates seemed to be a standard practice for 25 MU and the crates usually seemed to be loaded with unwanted junk. I once saw a crate filled with hundreds of meticulously packed small cardboard boxes (about 1.5×1.5x.75 inches) containing things like rubber glands and labelled with names like Airspeed, de Havilland and Gloster. Some one once bought a couple of large flat crates to make a shed and apparently became the owner of a couple of wing sections. Someone else bought a couple of long wooden trusses (handy for supporting a barn roof). I saw these. They were painted blue and bore serial numbers in white such as XL160 and, if my memory serves me correctly, also bore comments like ‘ Starboard drop tank’. This I guess made them part of servicing cradles for Victor underwing tanks.

However, I digress.

The mystery panel is about 11.6 by 6.7 inches. The dished hole means it is an interior item. It has a “clean” side (with the dish flange) and a “dirty” side (painted silver at least once) and lots of bolt holes suggesting perhaps it went in a “structural” location.
The dirty side has traces of perhaps as many as three inspection stamps, but only one really shows. That one has only a small part showing clearly and I cannot decipher it.
The bend at one end could be damage rather design.
The clean side has a minute number stamped: D00 4184-A0J.

So, any ideas as to what the panel is off?