Hi Adrian,
You're most certainly welcome...
I, too, have encountered at auction houses items with a similar background story to your own, with a claimed provenance of having been uncovered over the course of the Three River Gorges Damn Project. However, not one is uncluded among the aforementioned pieces I referenced in my first reply, as with the exception of one lithic, I sincerely doubt the authenticity of the others sharing the same background story. Don't get me wrong - I have no doubt that artifacts are uncovered on a routine basis, as this is the norm in any archaeologically-rich environment.
However, I firmly place my faith in the credo that you 'buy the sword, not the story.'
With regards to this piece, I cannot speak to the 'cleaned' surface... old bronze simply presents itself with too much variation - due to differing alloys, environmental conditions, etc. - to speak with any degree of certitude by looking at a photograph. However, the aforementioned issues provide enough visual clues to reach a conclusion.
With regards to the distortion of the metal as a result of corrosion, that's a first for me...
Like I said, I've seen delamination due to oxidation, but not
this kind of deformation. Let's hope one of our metalurgists can chime in on this.
Lastly, I rarely doubt the veracity of someone's claims on the face of the claim alone (or at least express my doubt on record), but I have to question your friend's claim that he is responsible for the artifact I highlighted in my earlier reply. I have a very hard time believing someone - anyone - cleaned out the channels of the face of the stone insert with
an electric drill and that the result just *happened* to present itself very similarly to every modern Chinese knock-off lithic I've seen in which electric drills were used to create the finished product.