The molten Zinc (Im guessing it is) that was put in the heat risers to separate the Two center exhaust bowls looks to have come loose...look at the "Black edges" around the silver in the center bowls.
I had something similar happen to me once years ago. I spent too much effort wanting to make that area look "too good" & blend in. The result was after years of use though. A small sliver had gotten hot on the edge & broke off, fell down in & did some not nice things.
Once the heads were off, I found another port was just about ready to go. A small tri-angle by the height of the bowl was cracked nearly to the top. I ground all of the edges back more "square like" flat & not worry as much about the cosmetic idea of it.
That was likely 10 years ago & many miles later with no farther problems. I looked at it as a learning experience, however mine was/is a low-buck self done deal...not a bunch of money paid out for a shop to do.
I have done several other heads without failure...some with Zinc & later aluminum (which I is safer) without issue. Lorne