The 'rivet placement' on this piece tends to be 'very poor' and does not come close to Lockheed production patterns on the L10 - it is distinctly 'hand craft' as if done in a pinch.
I do not believe we are going to find any patterns on this artifact that match any stock rivet patterns on the Electra - AE's or otherwise. That is one reason I have thought of this piece, IF it relates to NR16020, as a candidate for the covering over the large lavatory window. As best as I can determine (primarily by the Harney prints and texts therein) that window was covered in Miami before the last world flight attempt continued on its way. AE was only there a few days, and whatever covering may have been done, if that information is accurate, had to have been done relatively quickly. It may therefore be a candidate for a quickly done one-off piece-work job, complete with hastily added stiffeners (in Miami - or perhaps later if 'oil-canning' was noticed in flight along the way and dealt with later...).
The 'stiffener' lines (I don't know that they were present but the rows of #3 rivet holes is suggestive of light stiffeners) are consistent with that approach.
If that is what this artifact truly is then the only 'match' we'll get to factory rivet lines is where the panel may have picked-up existing rivets along the stiffener at the lower edge of that window, or next candidate possibly the forward row if it picked up the former / bulkhead flange on the forward edge of the panel. Otherwise, it is whatever pattern the installer established - and possibly matching any fastener holes used for the window edges if other stiffening / window bounding elements were placed there.
The window I speak of is plainly visible in many photos of the right-side of NR16020; it is also distinctly covered in later pictures by a panel of about the size of this artifact (the artifact fitting within the bounds of the visible panel - the artifact does not represent the whole of what it once was). 032" T would be a natural for that application, as would the lighter rivets for something like light-weight stiffeners installed behind such a large panel.
One key to better understanding what 'window cover' and details were actually on NR16020 at that place would be a good photo by which we could discern rivet patterns... so far I've not found one of that kind of detail.
So - IMHO, getting to a museum L10 might help as far as trying to match edge rivet patterns, but that is about it. This is a unique piece due to the irregular rivet pattern, wherever and on whatever it was installed. Factory metal work was far and away advanced enough by many years for that pattern to not be a product of any factory floor. Handcraft at a local shop for a quick cover job? Absolutely within reason. Question is 'what location' and most of all, 'what airplane'?
I still view NR16020's RH lavatory window (oversized - apparently for nav use and later not needed) as a strong candidate - but need information about how covered including pictures, if it can be found.
LTM -