@AtticRattata asks
sending two copies of the same card. How do I keep track of which one is which?
Jeff answers
I'd document each copy's visible distinguishing details and keep its position consistent with the submission paperwork, following the company's packing instructions. Don't mark the cards themselves. With very similar copies, good records before shipping are easier than trying to reconstruct their identities afterward.
— Jeff, infinitepulls.com