What is the purpose of the key closest to the head joint? It looks like you could almost build a Boehm flute from all the metal attached to this guy. I have to wonder what it must weigh.
a venting key for 3’ and 4’ octaves, :- )
since we, mostly plays irish music…don’t even know those kind of things 
)
That is not its primary purpose, though it may have auxiliary uses thus. Primarily it is simply a trill key for the (otherwise very awkward and unsatisfactory) D/Eb trill at the bottom of the 3rd 8ve. It doesn’t do very much else. It is pretty common on later C19th continental simple system + flutes like “Meyer system” and “Ziegler system” and the various “Reform” flutes etc - see Rick Wilson’s website for much more… I have French, Austro/German and Italian flutes here which have that key, and I have (though more rarely) seen it on pictures of English flutes, including R&R - they’d do anything to special order!
It’s also handy for playing the main theme from Il buono, il brutto, il cattivo.
Dude! I have that exact same nach Meyer B-foot model, with the same type of case and lining. 12 keyholes, 13 touches (2 touches for the Bb). Doesn’t play well in any sense, and the tuning’s wonky. Looks impressive on the wall, though.
Don’t remember how heavy it is, but I recall that it nevertheless seemed okay enough for balance.
I have an 11 key, including alternate Bb, model Nach Meyer that is my main flute and plays rather nicely. Bit heavy but well balanced and comfortable to hold. I use that bottom B more often than the trill key but the trill can be fun when improvising on jazzy blues stuff. The tone hole of the trill being so large and close to the ear makes it sound a bit loud when using it though.