Small size Federal Reserve Bank Notes were printed as an emergency issue in 1933 using the same paper stock as National Bank Notes. They were printed in denominations of $5 through $100. A National Bank Note has a line for the national bank's president's signature. The small size Federal Reserve Bank Note printed a bar over the label for this line, since Federal Reserve Banks had governors, not presidents.
The wording was also changed to add, "Or by like deposit of other securities" after the phrase, "Secured by United States bonds deposited with the Treasurer of the United States of America".
The twelve Federal Reserve Districts also appear on the bills as black alphabetically sequenced letters, from "A" to "L", a system essentially followed today on the $1 and $2 bills.
This emergency issue of notes was prompted by the public hoarding of cash due to many bank failures happening at the time. This also limited the ability of the National Banks to issue notes of their own. Small size Federal Reserve Bank Notes were discontinued in 1934 and have been no longer available from banks since 1945. As small size notes, they have brown seals and serial numbers, as do National Bank Notes of the era. But while they look very similar, and both have the words, "National Currency" across the top of the obverse, they had different issuers and are considered to be distinctly different types of bills.