In Photo One, showing the Hooven DF gear, at the left edge the portside cabin window seems to be lacking that bar or stringer. The Timeline for Dec 10, under the photo of the Cord and AE holding the cabin door partly open, with the dorsal antenna mast clearly visible, states the following:
"The bar through the cabin window (actually a stringer) was removed in January 1937 at the same time windows were added to the cabin door and right-side lavatory area."
If that's correct, it narrows down the time period for Photo One to the time after the navigation windows were installed.
I keep wanting to date Photo Two, with its Feature B round gizmo, as earlier than Photo One, which lacks that gizmo, though I cannot yet prove that. But there was ample time in December for Photo Two to be earlier, even if the dark vertical wire is lead-in from the dorsal antenna that was installed some time before that Cord photo in Burbank.