If your original statement was true, the current series would be 2013A. The only thing that changed on our notes between 2013 and 2017 were the signatures.
Reading is Fundamental. If your a little bit less critically analytic you’ll see that my first post includes “Or so I’ve been told”, qualifying that it may not be carved in stone. My second post states “NOT EXACTLY” ... “PRETTY MUCH” ... and “SIMPLER”. I believe the whole process was changed and set how it is today with some act in the ‘70’s. I’d guess at a year but I don’t want to be subjected to another factual firefight if I’m incorrect.
I like simpler sometimes and hey, I used to do government work also. The U.S. Army Corps of Engineers.