So, with one fell swoop of about 650 cards from a single set, we reach 20,000 cards in the 20 in 20 lot today, with still another 6-7k of cards likely still to go, so the lot was definitely underestimated when it was advertised, and when I bought it, and that ok with me!
The set in question is one there's been a number of already, and one I don't personally have any investment in keeping - 1992-93 Upper Deck basketball. More specifically, these are all from series 1. In all, it is a 513 card set (well, 510 with three redemption/"a" version cards included) and series 1 runs 310 cards in total.
With 600+ cards here, won't scan much of them, and can say it is not a complete set as some cards are definitively MIA, but we can hit a couple highlights, and examples of cards that there are, well, a few copies of.
These are all the draft picks included, and the checklist for comparison - no surprise the big names aren't here.
Another subset, just showing some of here...
These amount of dupes weren't the norm, but there was maybe a dozen cards with 8+ copies.