Posted By:
CoreyRS.hanusSteve,
To answer your question, I own one card that is in an altered holder. And I own a N28 set of 50, only the baseball of which are slabbed. I have not re-submitted those cards. The provenance of that set is that it came from a long-time collector who had it in his possession for many years, so I have a high comfort level none of the cards have been altered.
EDITED to add:
James, interesting though that in regard to the Lionel Carter collection, arguably the most significant offering of high grade post-war cards in recent memory, Mastro chose to go with SGC over PSA.