PJS
Sorry, sorry for getting back so late ....
Ken,
....very close !!! (you know my method and procedures very well!!!!

)
The procedure I followed to minimize the big discoloration is the following:
- Duplicated Background.
- Clicked on the Channels Tab.
- Selected Red Channel and run the Curves on it (Attachment 1)
- Selected the Blue Channel and repeated the Curves on it. (This procedure reduced the contrast and balanced Shadows and Highlights on these two Channels.)
- Still working on the Blue Channel where the discoloration is much more evident, I used the Pen Tool to select it (Feather: 6 pixels).
- Back to the Layers Palette, with the selection active, I created a Levels Adjustment Layer and changed the values in Red, Green and Blue Channel ... (Attachment 2) ... untli I got a result I could work on (Attachment 3).
After this, I proceded with my usual 'restoration' routine: Creation of several Adjustment Layers (Selective Colors, Color Balance, Brightness&Contrast) and new empty Layers (Blendings: Normal, Lighten, Darken, Colour, Overlay) on which I used Heal, Blur and Brush Tools to selectively correct and enhance the picture.
Neat Image to clean up noise and .JPG artifacts.
USM to lightly sharpen the image.
Hope this helps...