These FRBNs were an emergency issue intended to get more cash into circulation during the Depression. So the BEP didn't have the time to engrave plates specifically for FRBNs; they just used the existing National Currency plates, and instead of overprinting the notes with the name of some National Bank and the signatures of that bank's officers, they overprinted the relevant information for some Federal Reserve Bank.

That caused a minor glitch with the signers' titles. National Banks have presidents, but the top officer of a Federal Reserve Bank was (at the time) called a governor. So when the BEP printed the governor's signature on these FRBNs, they also had to overprint the title "Governor" and black out the title "President" that was already present on the National Currency stock.

The other signer is supposed to be the bank cashier, which title was the same at the Federal Reserve Banks as at the National Banks. Trouble was, the BEP didn't have signature specimens of all twelve FRBs' cashiers on hand. And because the FRBNs were, again, an emergency issue, the BEP didn't want to take the time to have the FRB mail them a signature specimen. Instead, if they didn't have the cashier's signature handy, they just substituted the signature of some other random FRB officer, requiring the title "Cashier" to be blacked out and replaced too.

Nobody was particularly happy with the appearance of the FRBNs, but they got the job done. The plan was that, eventually, the BEP would engrave new plates specifically for the FRBNs, avoiding all of the above issues. But in fact the need for the FRBNs didn't turn out to be as great as initially feared, and so the BEP already had quit printing them long before the new designs were ready. So they all look like this....