I asked the OP to send me the picture offlist.
Here's how I would replace it to its former glory:
First I'd take off ALL the old patina using that rotten egg-smelling
dip recently discussed.
Dip it and rinse it immediately. Then steam to remove any stubborn
bits, redip if needed and rinse.
Then I'd use a chemical antiquing agent. I use Griffith's Silver
because it also works on
gold and works with this technique better than Liver of Sulfur which
goes bad after a while in the bottle, and never covers evenly.
(BTW, with the Griffith's I pour as much as I need to blacken a
particular piece into a beaker of the correct size, then drop in the
piece (or place the piece in first and cover) the after the piece is
completely blackened, I pour the solution into another old
Griffith's bottle, and reuse that solution over and over until it
stops working, then discard it rather than polluting the new bottle
with the used solution.)
Then I throw the piece into my tumbler (I use this type:
and cannot imagine using one of those that are smooth inside like
rock people use) and with steel shot & tumbling soap, let it spin
When I took it out it would be perfect.