Condition Issue: What is it?

[mintacular]

Hi folks, I have a valuable post-war card with a condition issue that I haven't run into, wondering what might have caused it. If you hold the card on its side, it does not have a natural "curl" or straight 180 lie to it but instead small wavy effect (again I am describing the surface bend---NOT edges, trimming, etc.)...

When you feel the cardboard between thumb and index the surface feels like different indentation areas, your fingers drop down, and then up etc as you run fingers across card...

The card does not appear to have any water damage issues i.e. the feel and look of card does not appear to have absorbed water....The card was housed under a hard plastic screw down with no sleeve (I learned a couple years ago this is a bad practice) so I'm wondering if that could've caused this? The reason I think this did not cause this effect is that there is no surface wear and the uneveness of the "wave" effect would make me to believe there is something else going on....

Assuming you can identify the issue, how would a TPG handle this issue? Thanks!