In PA, there are numerical codes only, but it's not clear what they mean, if anything.
All scratch offs contain a QR code that can be scanned at digital lottery machines to either check or redeem, scanned via the PA Lottery app, or the small ticket checker at the counters of lottery retailers. These codes can tell whether a ticket is a winner. It is my firm belief that since if the code is damaged, it asks for the game number, the book number, and the ticket number that they essentially know when and where the jackpots are going to sell. They have to have some measure of accountability as to a book number was issued to a certain retailer.
I'm originally from MD, and I sometimes play down there. The QR codes on their tickets work the same way as PA's.
As pointed out in FL, books seem to be printed at higher numbers or excluding some numbers in PA as well. By knowing the number of tickets, we know how many books there should be for each ticket. I've frequently seen tickets at the end over those numbers. While there are certain places that do give you a good idea of how far into each game tickets are (by either the game disappearing or purchasing them and obtaining the book number), there are plenty of places that are selling old or even the first books they obtained. I am still finding plenty of my current favorite game ($500,000 Crossword Mania) with books that only have 4 digit numbers (below 10,000). The game is otherwise into the 70,000 book numbers (as high as 79,200) at busier retailers.
I have found some games seem to have patterns, although almost universally in PA, earlier scratch-off tickets do not seem to provide many jackpots. I am guessing the Lottery wants games to last a while so they can sell through more tickets. The only tickets that seem to produce some early jackpot winners (as in the first couple weeks after release) are the seasonal tickets PA does for Valentine's Day, St. Patrick's Day, Mother's Day, Halloween and Christmas each year.