I was organizing my collection the other day and realized I also have an original ARCO deck, shees - the D & D box looks so spot on, I thought I bought a dupe
I can tell that the deck on the left is a reproduction, but I don't think it was a D&D repro. The one on the right is a genuine article Arrco deck. The Ace of Spades codes are the giveaway.
The deck on the left was manufactured on the 12th week of 2011. The deck on the right was made on the 48th week of 2006. USPC in both cases, not Chicago made from the original Arrco factory - those are USPC codes. Arrco was acquired by USPC in '87. While most decks use a letter code in addition to the numbers, they've also started introducing longer codes or code variants.
For the deck on the left, "N" is the code used in 2011 (and a few other years as well, cycling in most cases about every twenty years), the numbering to the right has to do with some sort of inventory codes/manufacturing codes (much less important without access to the USPC database) and the four digits to the left of the "N" are the two-digit week number and two-digit year number of precisely when it was printed. For some reason, the '06 deck left off the letter codes and other codes, going with just the week and year. It's been known to happen - the codes are generally left off entirely for most custom deck orders and for decks that have "preprinted" faces, like most Congress decks.
In the case of a deck with preprinted faces, USPC will run off a large lot of playing card sheets, only printing the face side of the sheet, placing them in storage until the time comes that they need to complete the deck with a new back design, usually only requiring a portion of the stored sheets. I believe they do this to save time - they print the faces during some slack time between other projects, then when they need more Congress cards and they have a new design to use for the back, they bust out the pre-printed sheets. Preprinted sheets are also used, I believe, by Zazzle for their custom-made decks with USPC-licensed faces. The end result quality is nothing like a real USPC deck, but it's cheap and easy.