I believe that isn't correct. To check if a deck was really made in Ohio, you check the jokers, and I own a couple of decks that have Ohio boxes, Ohio jokers, and ohio deck, but with a black seal.
Don, can you help me out here?
Oh, so NOW I'm the man with the answers, eh?
To my knowledge, there are NO blue-sealed standard-issue decks from Erlanger. Show me a picture, if you would. Custom decks are a totally different animal - they can have any seals the designer's willing to pay for.
Now, this refers ONLY to standard-issue decks - see above.
All modern decks from Kentucky have black seals. Period.
Earlier decks from Cincinnati used blue and red seals, blue most recently. Towards the latter part of their run in the Cincinnati (Norwood) plant, they switched to black seals. It seems more price-effective to use just one color instead of multiple colors.
As the transition took place, there were some decks in Cincinnati boxes that were manufactured in Cincinnati, but some in the same boxes that were made in Erlanger. A Cincinnati box is no guarantee that it's a Cincinnati deck - IF the box has a black seal. Blue seal and red seal decks were indeed from Cincinnati. You can tell the difference by looking at the address on the guarantee Joker.
I bought some Cincinnati-boxed, black-sealed Tally Ho decks. The guarantee Jokers had the Erlanger address on it - so they were Erlanger decks.
Most if not all of the Cincinnati boxes used to pack Erlanger decks were used during the transition period and the "shakedown" phase of the Erlanger plant, which was rough for about the first year-and-a-half. Decks from Erlanger made in 2009 and 2010 are more likely to be of lower quality. But the new sheet-fed press at Erlanger can beat the pants off the old dinosaur sheet-fed press they retired in Cincinnati, resulting in superior quality cards from Erlanger, despite some claims to the contrary, once the shakedown ended by about the beginning of 2011.
The week and year of manufacture would be revealed in the Ace of Spades "letter code". Recently, USPC added a four-digit number that appears BEFORE the letter in the code. The first two digits are the week of the year the deck was printed and the last two digits are the last two digits of the year. For example, a letter code of "1111-N2325H" - which is the same code on a pack of Tally Ho circle backs with a black seal in a Cincinnati box - would have been made in the 11th week of 2011, or around mid-late March. Standard Bikes and Bees are probably out of the Cincinnati boxes by now, while Tally Ho decks have lower overall sales because they're consider "regional" and are only generally sold in magic shops or stores within New York City, so you'll find newer, better-quality decks still appearing in Cincinnati boxes.
Some decks are "pre-faced", mostly in the Congress brand. This means the sheets are pre-printed with faces and the backs are left blank for later printing with whatever styles are that season's choices. Those decks won't have an AoS letter code on them, since they're manufactured on two totally different days, perhaps weeks or months apart from each other.