CUSIPs are a 9-digit alphanumeric code for uniquely identifying a financial security. https://en.wikipedia.org/wiki/CUSIP They were invented in the 1964, and given the reliability of data transmission in the 60’s, the 9th digit is actually a check digit used to confirm the validity of the first 8 characters. Sometimes, even today, you might find reason to want to validate a CUSIP,