Yeah the zazzle thing was what I was trying to get at, but had forgotten the name. Cheers for clearing up the difference Sir. Donald
My title is Discourse Moderator, not Discourse Nobleman! And my rank is Platinum Member, not Knight of the Order!
Those blanks I referred to are uncut sheets that are only printed on one side. It's the reason why there's no letter codes with the Ace of Spades - when the faces are printed, there's no clue as to when the backs will be printed so no date is indicated.
They do the same thing for all of their Congress decks - they haven't had date codes on them for a few decades. Makes it harder to date a deck of them, but makes it easier for USPC to almost print on demand whatever back they want without even needing to think of the faces.
They might make a million blank Congress decks at a run, and they sit on a warehouse shelf waiting for the next stage of the process - in fact, they might not even cut the paper roll into sheets, instead rewinding it onto smaller rolls of maybe 100,000 decks each. They can leave a roll in the "Congress printer" and they're ready to fire it up and print backs at will. It also means that the printer used can be smaller (since it's only used for bridge-sized decks) and doesn't have to do double-sided prints, which probably makes it less expensive.
It's possible they would use a sheet-fed press for it, but I'm thinking that due to quantities printed, they may use a web press or something similar designed for one-sided printing.