Posted By:
runscott...and only because it was so damned ugly.
1) I wrapped a thin terry cloth around my forefinger, dipped it occasionally in warm water, and rubbed gently on the glue/paper residue areas. It worked well, but I had to be very careful about the amount that I soaked each area, and how hard I rubbed. The only unintended result was that there was some discoloring of the dark mat where I used too much water, and if I soaked an area too long or rubbed too hard, a little of the black mat paper came off.
I don't think David is going to like this, but...you can "blend" some aberrations on these old mats just by rubbing with your fingers - the oil in your skin does the trick. I do this all the time and it is completely unnoticeable.
2) Some previous owner had darkened parts of the actual white photo border with a lead pencil. Very, very odd. Anyway, I simply erased it with an art gum eraser.
3) I was joking about trimming and painting it...but I did originally give it consideration, thinking the picture might be beyond saving.
I have found that #1 above works well for normal baseball cards also.