The star in the serial number on 1963 US 10 dollar bills signifies the bill was part of a special series issued in 1963 to commemorate the 100th anniversary of the issuance of the original $10 bill in 1863. These bills were known as the "1963 Blue Seal Series" and were printed with blue seals and serial numbers that included a star (*) as a prefix. The star denoted that the bill was part of this unique commemorative series.