On Benjamin Franklin's lapel on the 2009 Series A.

If you refer to the text in the top left of the obverse of the current Five Dollar note, "FIVE DOLLARS" is written about fifty-five times in nine rows of teeny weeny microprinting.

The small fine type on currency that makes it difficult to read is called microprinting. It is a security feature to prevent counterfeiting by including tiny text that is hard to replicate.

The paper is made of a specific blend of materials, bills often contain security strips and watermarks (visible when held to light), parts of the design have microprinting that blurs in counterfeits, and some of the ink shifts colors when viewed from different angles.

Watermarks, security strips, and microprinting weren't introduced until the 1990 "big head" redesign.

Older bills have very few anti-counterfeiting features. The most obvious is the presence of small red and blue fibers embedded in the bills' paper.