Lot's of good research on this thread. You guys are awesome.
To summarize, here's what November 1936 looks like so far:
Sat., Nov. 7
AE is on the east coast. The airplane is in Burbank. She attends the Notre Dame - Navy football game in Baltimore.
Tues., Nov 10
AE writes a letter to FDR from the Putnam Building in Manhattan.
Thur. Nov. 12
AE does a speaking gig in Pittsfield, MA.
Sat., Nov. 14
AE does a speaking gig in Syracuse, NY
Thur., Nov. 19
AE has returned to the west coast after "an extensive lecture tour" and leaves Burbank with GP and Bo to fly the Electra to New York "for adjustments to the plane's radio apparatus." On the way, they'll stop in South Bend, IN for a meeting with Vince Bendix.
Fri., Nov. 20 or Sat. Nov. 21
AE, GP and Bo arrive South Bend.
Sat. Nov. 21 or Sun. Nov. 22
AE attends Northwestern - Notre Dame football game with Vince Bendix.
Mon., Nov. 23
AE and company fly the Electra to New York. In "The Mystery Solved," Elgen Long wrote (page 60) that Earhart was in South Bend to seek sponsorship from Bendix and came away with "a promise of $5,000 and some new Bendix aircraft radio equipment." Unfortunately, no source is cited.
Wed. Nov., 25
AE has been in New York sitting for a portrait that will appear in McCall's magazine.
Fri., Nov. 27
The airplane is inspected by the Bureau of Air Commerce at Roosevelt Field, Garden City, NY
Sat., Dec. 5
Earhart leaves New York to begin a "leisurely flight" back to Burbank accompanied by Jacki Cochrane. We don't (yet) know whether the trip included a stop at Purdue. Such a visit would logically have been on or about Dec. 6 or 7. A photo of the plane anytime during the trip back to Burbank would be important. The dorsal vee antenna does not seem to be present when she stops in South Bend. Was it added in New York?
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So the airplane is in New York from Monday, November 23 until Saturday, December 5. - 13 days. It seems likely that whatever "adjustments" were made were done in the three days (24th, 25th, 26th) before the airplane was inspected on Friday, November 27.