I'm thinking it's USPC. Based on your description, the cards are exceptionally slick - a sure sign of Magic Finish. I'd go further and say that the stock is Bee Casino, since your description of the paper's firmness matches that of Bee Casino decks. One way to tell for certain, if you haven't already noticed, is by smell - Magic Finish has a distinct smell; it lasts for a good while after the box has been opened. Compare it to off-the-shelf Rider Backs or Tally-Ho decks.
How the heck do you know so much?! Been reading your other comments too and your knowledge base/bullshitting skill is very impressive!
What do you guys think of the marking system?
Both learning and experience. I'm friends with a few people in the business and I'm a good listener!
Couldn't tell you about the marking system yet, unless it's the same one he used for his Madison Players over at T11. If that's the case, it's OK, but it's annoying to have to learn a new system. My preferred marked decks are the Ultimate Marked Deck and the GT Speedreaders. I do also have a fondness for the Gambler's Decks.
UMDs were the bomb, but they're out of print now. Printed on an altered Bicycle Rider Back in red and blue, the marks required no system to learn - they could be read as easily from the back as from the front, and even at some distance - across the table, if the table wasn't too big. These days, it's hard to find them for less than maybe $40 a pack - they're not only out of print, but they're also never to be remade. In order to legally defend the Rider Back design as a trademark (since the copyright expired a long time ago), USPC Legal no longer permits any alterations aside from color changes of the Rider Back, Bicycle jokers and Bicycle Ace of Spades.
The GTs are nearly as good. They were built on the Mandolin Back design - one of two designs USPC uses specifically for magicians to create gaffs with, they're close enough to the Rider Back that a spectator will likely not notice the difference while different enough to not dilute the Rider Back trademark. The GT decks, however, are almost useless for gamblers. The markings are in the top-right and bottom-left of the back, and they're inverted from what you'd expect - they're meant to be read easily in a spread where a spectator can see the back of the index corner, the traditional place for deck markings. They look at the corner closest to you, but find nothing, because there's no marks to find; you look at the corner nearest to them, you see the marks, oriented so you can read them easily.
The Gambler's Deck, however, is a unique piece of work. Originally, you could get them in Rider Back; after USPC Legal stepped in, they were made in a generic back that no one liked. Today, they're made in Maiden Back (the other alterable design that looks similar to Rider Backs, and if you ask me, the more attractive of the two). For all its different designs, the deck had three features: a) it was marked, and in over a half-dozen different ways; b) it was cut to be a stripper deck as well; and c) it was designed (and numbered) to be used in a specific stack order. Among other things, when correctly stacked, you could cut the deck to any point, look at the top card and know what the BOTTOM card was without even memorizing the stack order, thanks to the multiple markings. It is a fun deck to play around with - I use it in conjunction with an Invisible deck for some great effects - but I don't think it would hold up as well under close scrutiny; the marks are hidden, but there's so many of them. It would never pass a riffle test. (Hold a pack of cards face down, riffle the cards like a flip book and look for any "flickering" - that's the giveaway for most marked decks that don't use special inks or daubs. That's the riffle test.)
Which brings me back to the Madison decks. While it is a nuisance to learn a marking system, the Madison Players were the first marked deck I've seen that are so subtly marked, they could pass a casual riffle test. They wouldn't hold up under closer scrutiny, but the marks are small enough that you can actually miss them with a simple flip-through. So if this deck uses those markings, AND it has this Bee Diamond Back-like small, repeating pattern to it, I'm thinking this would pass a riffle test even more easily. Those backs are practically like looking at an optical illusion in the first place.
