I believe we have to be thorough about eliminating other potential sources for 2-2-V-1, and a potential 'donor' 350 miles away is strong, IMO.
Now lies this PBM wreckage with a stiffener arrangement of some sort visible through a gaping hole cut in the side of a PBM wing float where metal was removed... The history of this wreck is colorful - deliberately beached on coral and destroyed by fire - and by the old repairs visible on the float, 'hard service' suggests a history of dings and patches.
While later than the Electra, the PBM is arguably of appropriate vintage (entered service September 1940) as we now understand the decline of the brazier-head rivet to be about a decade later than previously thought, and that some of these seaplanes had surprisingly thinner metal on the hull skins that previously believed (see links up-string).
"...someone 'cut' metal from the side of that float - and a bit crudely, look at the jagged edges - and must have gone to some trouble to do so, for some reason."
So we have vintage-reasonable wreckage within 300 miles or so of Gardner which bears evidence of old repairs and later 'harvesting' (my term) of some portions of metal from the remains... My belief is that we cannot ignore this hulk as a possible source anymore than we'd shy from visiting the AF museum for a comparison.
Jeff, I agree the PBM on Howland Island is still in the running as a potential donor. Ric's list of "Aircraft lost in the vicinity of Nikumaroro" includes another PBM that "Hit reef while taxiing at Canton," on Dec. 15, 1942. That is an interesting lead that should be looked into carefully. An accident report probably exists somewhere.
You are an excellent finder of stuff, Mark - can you perhaps locate such a report?
Maybe more to the point of the PBM - which I agree circumstances make intriguing - can you find technical specifics as you have on other types like the PBY and B-17?
I say by 'circumstances' because we have visible PBM wreckage within an arguable 'reasonable distance' of Niku with very suggestive repair / salvage evidence showing. But will it stand the scrutiny of technical data? The review of the PBY data revealed much heavier construction throughout, and a lack of the appropriate rivet type. Although we now know a brazier might have been substituted for other types in a repair scheme, not so much so smaller than original rivets.
The PBM would have to carry #3 rivets in original structure to be convincing. Having now seen how the PBY is built, I have my doubts. But we have a surviving exmample at Pima - and perhaps the manuals, if you can find them, may tell us something...
http://tighar.org/wiki/Aircraft_lost_in_the_vicinity_of_Nikumaroro
You bring up a very interesting question; who could have removed that piece of metal from the float on Howland Island? The island was un-occupied at the time that PBM was beached and burned.
"Anyone" could have, one supposes; it is intriguing to think of Niku islanders doing so, but I'm not sure we're there yet on that.
I've found some information about the skin plating on the PBM-5. As in the case of the PBY, it turns out to be thinner than might be expected. I suspect the 'hull side and crown' had large areas of .032 material. The wings may also have .032 skin plating, but this report does not go into that unfortunately.
"...Plating on the bottom of the hull from the bow to the main step is varied from .051 to .072 in thickness. Afterbody bottom plating varies from .040 to .051 in thickness. Hull side and crown skin varies from .020 to .045 in thickness."
Design Analysis of the Martin PBM-5 Mariner
http://legendsintheirowntime.com/PBM/PBM_IA_4509_DA.html
Interesting photos of a PBM wreck in Truk Lagoon can be seen here- (No, I'm not proposing 2-2-V-1 came from this area- I believe it most likely came via Canton Island- where aircraft wrecks were probably piled high.)
http://warbirdinformationexchange.org/phpBB3/viewtopic.php?f=3&t=17105
Interesting, but essentially anecdotal (like so many things, I know) - now if we could just find more specifics...
As to the PBY, it didn't pan out so well in my view: while some light plating is there in places, the rivet sizing and type is way off.
Specifics needed. How far are you (or any reading this) from Pima? There sits a PBM... I think the sole survivor, in fact.