OK I know nuffink about plane construction but if you were covering over a window would you cut it to shape as an insert or would you just lay it over the aperture?
It can be done either way, depending upon need of function and / or expediency.
Earhart's window covering appears to be 'expedient', as best I can tell from the pictures we have - a mere covering that neatly enough simply overlaps the original skin on the Electra at the edges of the aperture. It also has distinctly 'square corners', not the nicely-rounded radii of a 'plug' for that window. Admittedly those photos are a bit grainy, so take with a grain of salt.
So it does not seem to be a 'neat' plug or insert, such as is the case with the Finch Electra on display in Seattle at the Museum of Flight (I have pictures but not at-hand for moment - will follow). Finch's window 'covering' is fairly clearly a removable 'hatch' by appearance, with a distinct separation line; the outer air passage (skin) is flush to the surrounding skin. It is also clearly vertically braced in the web area (major 'mid' or 'open field' between the boundaries). As a 'plug', it also happens to have rather elegantly radiused 'corners' as opposed to the rather sharp corners on the Earhart airplane covering (which CAN be discerned clearly from the vintage photos). 2-2-V-1
clearly does not match the Finch airplane; it
appears to be a possible candidate for the Earhart window covering, IMO.
What we cannot tell from the existing pictures found so far of the Earhart Electra window covering is how any mid-field rivet patterns are oriented - vital to the case for 2-2-V-1, obviously. But it looks to be braced rather 'normal' to the surrounding skins (which arguably suggests a stiffener pattern more closely oriented to the existing longitudenal stiffeners on the bird rather than vertical to my eye - but can't be sure). It also lacks the tell-tale gap around the edges that are noticeable on the Finch bird (no pun intended...) in the 'plug type' installation. The bracing does not mean it would match existing 'stiffeners' in the Electra because, IMO, these could have easily been improvised as mere mid-field light-weight stiffeners to avoid the timpanic oil canning effects of airflow over a large, thin sheet. That is of course speculation since so far we don't have details - but it is quite possible and a realistic position to explore, IMO.
I wouldn't know how to lay odds on this, but as Monty notes, I have a very strong 'hunch' about the possibility. I realize there are still other mysterious questions about this artifact - some that may yet disqualify it. But it has not been qualified as from another type as-yet despite a rather exhaustive effort (I was certainly exhausted after crawling around a number of museum pieces with TIGHAR in Dayton...), and this possibility seems vital in my view.
There is another string that was devoted to this prospect. Go there to review previous discussions. I closed that string after the focus shifted to the belly as it was believed that the rivet pattern was not right for this - but I'm not sure we really connected the dots on that at the time, and the belly was a good focal point for study (there are surviving examples of belly skins, whereas Earhart's window covering was a 'one-off' effort which wasn't duplicated among sister ships that we are aware of).
As to Nathan's suggestion (welcome aboard, Nathan) regarding possible stowaway on the N.C., I doubt it (and those who adhere to the font mystery as disqualifying would howl in agreement, I'm sure) - 1929 (year of ship wreck) was too early for this kind of material to show up as relating to aircraft construction. The Boeings of the time ('29) were rag, steel and wood - the B247D didn't emerge for a few years yet (and would be the one Boeing product of the '30s that might contribute such an artifact). I would put 'other airplane types' in the area before that (and the question remains: WHICH other types? A Cinderella hasn't been found for this aluminum slipper yet...).
I'd like to encourage our followers to scour for a good picture of the covered window on Earhart's airplane - Niku enthusiast or critic matters not (some of our critics appearing here have contributed some outstanding finds and all of us at least share an interest in this quest, either way). I wish I were as good at ferreting those things out as so many others have been, but just don't seem as able as some, so contributions of such pictures are asked...
Here is one from TIGHAR's files -