I believe it is safe to assume that Fred Noonan had a Sextant or Octant on the last flight. Some folks think he had two, but the actual evidence of a second one on the Earhart flight is not well supported.
Harry Manning loaned FN a US Navy Pioneer Bubble Octant, #12-36, in a letter (edit: actually a note, see reply #2 below) dated March 20, 1937. (
http://tighar.org/wiki/File:Noonan_Octant_Receipt.jpg) It may be the one used on the last flight.
Gary LaPook posted pictures of Harry Manning with a Bausch & Lomb model A-6 octant, showing it to AE (Gary - do you know the dates of the photos?). It may be the one used on the last flight.
Helen Day, a friend of Fred's, noted that he had in his posession an octant box (Re: Why wasn't Gardiner identified in the radio messages? Reply #132, in which GL references "East To The Dawn", by Susan Butler). It may be the one used on the last flight, and may be one of the ones mentioned above.
FN loaned a sextant to W. A. Kluthe, "...who at that time was studying navigation under Mr. Noonan in preparing for service in the Pacific Division of Pan American Airways, for use in practice praticle [sic] navigation." (TIGHAR TRACKS,Vol. 14, No. 1). It was NOT the one on the last flight - it's at the National Museum of Naval Aviation in Pensacola, Florida.
Some folks go out on a limb and suggest that a second sextant on the Lockheed was the source for the box that was reported by Gallagher on Gardner in 1940. This may be backward reasoning, assuming the presence of a second sextant to explain the box reported by Gallagher that proves AE must have landed on Gardner. Forward reasoning would begin with what is known of the boxes on board the Lockheed, and trying to match them to the box reported by Gallagher. After all, we KNOW that Fred had an Octant or Sextant with some kind of protective box, but we don't know what sort of box it was.
A separate thread is working to identify what Sextant was assigned to the box reported by Gallagher, so let's let that approach work its way through. It might converge on what I'm proposing here, or might not.
The 1930's was a time during which Aircraft Sextants/Octants rapidly evolved, from modified open-frame "marine" sextants, to completely enclosed hand-held machines. Their cases, or "boxes", also evolved during this time, from a low-profile "flat" box, typical of all previous marine sextant cases, to tall-profile skinny boxes, now generally associated with anything called an aircraft "Octant". There was a transition period in the early-to-mid 1930's when Octants used low-profile boxes. Such a box might be likely to be identified as a "sextant" box in Gallagher's report.
Let's explore what we can about the known and presumed sextants, octants and boxes used by Fred and likely to be on the flight and/or on Gardner island. This approach might rule out Gallagher's box as belonging to the Earhart flight.