Photograph identification

While we're still on the subject of the orange toned photograph, and,
strangely enough, since I discovered the item today, I'm really rather
excited to contribute this one.

The item is one of the Gardner albumens of the Gettysburg battlefield,
specifically the four dead soldiers, already bloating from
decomposition. Really rather a gruesome photo, but famous.

It is definitively original, with the appropriate mount.  It has been
flat filed in an acid free folder, a rather nondescript chromolithograph
stacked on top.

(Not my idea, folks.)

A large orangish brown stain has formed in the middle of the photo,
irregular in shape.  The edges of the photo retain their original tone,
with no evidence of the Maillard effect.  Shadows have a distinctly
purple tone.

The stain has not migrated through the mountboard, but DID migrate into
the litho above.  More, portions of the stained albumen show texture,
that seems to match the litho surface, while the stain on the litho
roughly conforms to the shape of the deepest area of stain on the
photograph.

There are two areas of staining; one, central, is quite brown, but with
an orange tinge, the other, surrounding the deep stain, is rather
vividly orange, with suggestions of burnt umber.  Shadow detail is
retained.

I am guessing retained fixer, activated at some point by high RH.
However, it is quite unlike anything that I have seen in our
collections. It's obviously irreversible, so I'm mostly interested in
the puzzle.

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                  Conservation DistList Instance 5:26
                 Distributed: Sunday, November 3, 1991
                        Message Id: cdl-5-26-005
                                  ***