Desert water bags conveniently explain why no canteens were found by Gallagher, but is there evidence that AE and FN carried them on their flight?
Convenience has nothing to do with it. We're simply trying to think of possible sources for corks with brass chains but no reported remnants of containers (aside from the Benedictine bottle).
As for the corks-and-chains, if the castaway arrived by lifeboat rather than be Electra, the corks-and-chains could have been from the water cask in the castaway’s lifeboat.
True, but where are the remnants of the cask? And where is the lifeboat?
BTW, here's the desert waterbag you asked for. Unfortunately no stopper is visible. We're not sure where or when this photo was taken. The mechanic's coveralls seem to say (something) Canyon Airlines. This could be the stop in Tucson on the way to Miami for the second attempt.
Very good, we can see a water bag all right. But in your previous post you said “
...corks with brass chains imply at least two stoppered containers...”. I only see one water bag, and I don’t see any corks with chains. Do you have evidence that these kind of bags could have come with cork stoppers and brass chains, or would they have been screw caps?
I’m certainly willing to agree that AE and FN could have brought water bags along with them on their last flight based on that photo. However, I can’t picture Fred and Amelia taking swigs from that water bag while in flight, can you? So I’m still wondering why no canteens were found at the castaway's last camp. Surely Amelia and Fred didn’t fly for 20 hours without rehydrating. If some forum member can figure out what 'type 4N' and 'type 6N' canteens were made of I think that would great. Aluminum canteens would certainly persist for many years (and I still think steel canteens would be in pretty good shape after only 3 years).
Ric, you ask where the remnants of the cask and lifeboat are (or were in Gallagher’s time). Um, may I remind you that you believe that the Electra landed on Gardner and essentially disappeared into the sea with nary a trace?...you want me to believe that Gallagher missed an entire airplane but he must have seen a little ole lifeboat and water cask?

...Seriously, there are all sorts of possible explanations, aren't there, e.g., the lifeboat was left by the shore, perhaps it was even holed during the landing, and it eventually broke into pieces; the water cask was left at the castaway’s ‘camp zero’, which is not the camp where he died. Once the cask was empty, it was of little use to the castaway, except for the cork and chains, which were used for fishing, so the cask was left behind at camp zero. Perhaps it was eventually found by the colonists but considered unremarkable. Perhaps the water cask awaits discovery at the castaway's camp zero somewhere on Niku.
=====
added later: Incidentally, Ric, you speculate that the photo you attached in your post was taken in Tuscon, I think because the man's overalls say (something) Canyon Airlines. The film clip from the Critical Past web site that I linked to above is said to have been filmed in Oakland on March 17, 1937. The description of the clip says: "
Earhart and Mantz begin weighing each piece of equipment, while George Putnam records the weights. Mechanic Bo McKneely appears in white coverall, with "Grand Canyon Airlines" written on back.". I don't know if what Critical Past says is correct, but if it is, then perhaps your photo wasn't taken in Tuscon.