Ric , mentions that air vents are noted in the Harney drawings, and they do appear to be drawn in similar design to the one we see in the photos. ( see attachment). I don't believe there was a similar air vent over the added large lavatory window that would have to be removed. As far as why the object appears to change shape ( to me) in several photos, I am just guessing , but was wondering if something was attached over the original ( sand casted aluminum piece?*) to provide a more atheistically appealing appearance, and that may have proved fragile.
* My guess by appearance in Amelia alone photo, posted by Ric.
P.S. Does anyone know the purpose of the little ball near Earhart's feet?