When the BEP was transitioning from large size to small size nationals, they realized they could stockpile paper with the central elements already printed. When a national bank placed an order, they created a plates with the title, signatures, and charter numbers.
The BEP had the paper already on hand and used it when they printed FRBN's.
Here's a Type 1 National Bank Note from my collection

The BEP had the paper already on hand and used it when they printed FRBN's.
Here's a Type 1 National Bank Note from my collection





















