Glue discoloration into the bottom flap on the back
I have some FDCs from several years thru the ages, most are from mid to late 70s.What is happening is the glue that is used on the bottom flap that folds up on the back is changing color on the flap where it is glued. I don't think these have been exposed to direct light or sunlight. The older gentleman I bought them from had most in the mailing envelope they came in.
2 questions: First, will this cause a drastic price drop (not that these are worth much, I paid him $1 each for what he had. Second, is there something I can do to get rid of it. Any type of professional conservation would be worth multiple times more than the envolope.
Anyone with any thoughts, suggestions or comments are appreciated. I guess I could just replace it with a new one.