US Fractional Currency - Second Issue (1863-1867)

5 Cent Washington in Bronze Oval Frame, Red Back with "18-63" Surcharge (FR 1233), 

PMG 62EPQ

Surcharges: Numbers (and sometimes letters) were printed on the back corners of these fractional notes. These were called "surcharges". According to Q. David Bowers, author of "The Whitman Encyclopedia of US Paper Money," surcharges are believed to be a reference for the type of paper used.