I have seen this little attachment on various photos of flutes, up near the barrel, but I can not find any information about it on google.
That is a LeFreQue sound bridge. There is a thread on the forums about it:
https://forums.chiffandfipple.com/t/lefreque-what-the-heck/95122/1
I use one on my “silver flute” - it does seem to improve the sound a little (for me). Seems a little more focused and the low end sounds a little more full. Many people diss it as a stupid gimmick, but I ordered one to see if I liked it (fully expecting to return it), and DID like it! Have not tried on my wooden or delrin flutes and don’t plan on doing so as I don’t think it will do anything for them and I don’t want to mar the wood (or delrin).
Pat
EDIT: Oops - looks like I kinda duplicated what I said in the other thread!
Ah so is that like those mystical phiton resonators?
Same sort of notion, I think.
And as was probably discussed in the older thread about the LeFreQue gizmo it is always difficult to really judge these things. Confirmation bias is a powerful force in human consciousness–I’ve seen a lot of it as a flute maker. Humans generally experience (or hear) what they are expecting to hear. If you say, “This gizmo will improve your sound in this way”, or if some influential players give a testimonial for something it can really bias our perception. I’m not saying this is good or bad–merely an interesting aspect of human perception.
This is an interesting article about a blind study conducted with modern violins vs. the much-lauded and massively “mythologized” Stradivarius violins:
And to repeat what I’ve said many times in the past, perception does matter. I think it matters more than empirical evidence. And while I might find it slightly frustrating as a maker to encounter players who put a great deal of emphasis on the material when I feel it is not as important, I’ve come to accept (and even support) players who do have those beliefs. If the LeFreQue gizmo gives a player a different experience that they like then I’m all for it. Sales gimmick? Perhaps. But trying to determine where measurable effect ends and personal belief begins is an unsolvable mystery 
The sad thing is those Phiton resonators are incredibly expensive! You could probably get a clarinet for the price of some of them.