Just a few thoughts as a starter.
Jpegs are 8 bit so I think I would up the precision to 16 bit Image -> Precision.
Maybe fix the tears and scratches before anything else.
I quite like the old faded tint, but a Colors -> Auto -> White Balance changes that.
Using duplicate layers with layer masks to separate the areas,
Two sample points, one vertically above the other, in a similar section. see: https://docs.gimp.org/2.10/en/gimp-sampl...ialog.html The sample point dock is in Windows -> Dockable Dialogues. Detached here for ease of use.
Then using the curves tool and each color curve in turn (Red / Blue / Green) try and match the value in one point with the value in the other point. You might get a reasonable match.
Come back to it after something else. A little post cloning and a sharpen
Jpegs are 8 bit so I think I would up the precision to 16 bit Image -> Precision.
Maybe fix the tears and scratches before anything else.
I quite like the old faded tint, but a Colors -> Auto -> White Balance changes that.
Using duplicate layers with layer masks to separate the areas,
Two sample points, one vertically above the other, in a similar section. see: https://docs.gimp.org/2.10/en/gimp-sampl...ialog.html The sample point dock is in Windows -> Dockable Dialogues. Detached here for ease of use.
Then using the curves tool and each color curve in turn (Red / Blue / Green) try and match the value in one point with the value in the other point. You might get a reasonable match.
Come back to it after something else. A little post cloning and a sharpen