Can anyone recommend a permanent marker which will write on a high gloss UV coated card stock?

Answer 1

No matter what type of ink you use you will have to be careful of the signature smearing. Be sure that the signature is fully dry before putting it in a protective sleeve or card holder. After the card is put into a plastic protector, keep in mind that if the conditions are not right the signature could sweat onto the plastic.

The ideal conditions for display would be indirect lighting, at a room temperature of 65 - 70 degrees F., and 50% humidity. Always check your signatures periodically for signs of fading or deterioration, and avoid excessive handling.

You might want to reconsider having the Baseball card signed. Signed baseball cards have a lower value than a signed baseball. The signature could also lower the value of the card. The signature would be considered a flaw in the condition of the card, and might sell at a lower value than an un-signed card.