I think that the Desert shield cards are associated with the base glow backs while the Tiffany cards are associated with the base no glow backs. I'm seeing the association with several of the base variations.
A couple of examples are- on #744 Nelson Santovenia with all the glow back base and Dessert Shield cards part of the S in totals is missing while all of the no glow base and Tiffany cards have the full S. Another example is the subjects found with the dark "hash mark". On the subjects that are found both with and without the marks the ones without the marks are only found on some no glow base cards, with those subjects the Desert Shield cards have the mark and the Tiffany cards don't.
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It could turn out that I'm wrong about this but what I'm seeing so far indicates there is an association with the variations that I've checked.