Timeless in Texas Letter perfect: Decoding Social Security ‘claim’ numbers Social Security recipients’ claim number is simply their own Social Security number with a letter symbol following it.

Old phone numbers in the U.S. had letters to denote the telephone exchange that handled any given number, a practice that lasted until the late 1970s.

Before that, three letters and four numbers were used. The phone exchange was prior to area codes and prefixes. The exchange names did more than provide a phone number.

And the numbers and letters you see on your boarding pass are no random combination. Every airline uses a specific system to ascribe letters and numbers to every flight.

When Mark Hauer lived in Colorado in the 1970s, you could tell which county a car was from, just by checking out its license plate. That’s because plates all started with a two-letter code based ...