When is a dollar worth more than a dollar? The answer is when it is a "fancy" note like a repeater, a ladder or maybe even a flipper.

For a niche of currency collectors, the value of paper currency goes beyond that assigned by the full faith and credit of the U.S. government. These hobbyists appreciate-and often put a premium on-the string of digits in the serial numbers that every bill of every denomination has.

Low serial numbers-think 00000001-are a favorite among the group and have some of the loftiest values, sometimes in the thousands if the condition is top-notch. But fans of fancy notes also look for all sorts of other configurations and curiosities that go by a variety of names. There are radars, like 12344321, where the digits read the same both ways as with a palindrome; repeaters such as 20152015, in which the numbers repeat in some fashion; solids like 77777777, which speaks for itself; and ladders like 12345678 where the digits ascend, or descend as the case may be, in order.

These notaphilists-as currency collectors are broadly known-have largely remained on the fringe, buying and selling among themselves via fan forums on the Web and scoping their wallets for finds. But the hobby has had something of a star turn over the past year, with attention from the likes of late-night TV host Stephen Colbert stirring up interest from treasure-seekers looking to cash in on their cash.

"I had no idea you could get rich collecting money," Mr. Colbert quipped during a spoof segment on fancy serial numbers in early November.

While Mr. Colbert was using the hobby as a punchline, it is simply a fun pastime for most collectors that does, for some, provide a modest sideline to finance their pursuit of notes.

"I thought the Colbert bit was funny, even though it's always a little painful to have people mock your hobby," says Dave Undis, a longtime fancy-serial enthusiast who has written about the hobby and runs CoolSerialNumbers.com, a website dedicated to fancy bank notes.

"People see stuff like that and they start looking in their wallets and start thinking they're going to get rich," says the 61-year-old Mr. Undis, a retired insurance executive in Nashville, Tenn. "If you go in as an investment, it's probably a mistake."

To be sure, some notes can command significant premiums. Low serial numbers often carry the best values for their popularity. One example: A seller on eBay recently was asking $114.99 for a professionally graded $1 bill with the serial number 00000046.

But most fancy bills trade only slightly above face value. And many of the most sought-after by collectors really have only sentimental or personal value, like their child's birthday or an anniversary (04072004, say, for April 7, 2004); ZIP Codes (00090210, where the final five digits in this instance represent the postal designation for Beverly Hills, Calif.); tombstones (19182014, here representing the birth and death years of a long life as they might appear on a gravestone; and others known by such names as Fibonaccis after the mathematical sequence and flippers whose digits look the same right-side up or upside down.

This collecting niche hasn't gone unnoticed by the government. The Bureau of Engraving and Printing sets aside some choice notes-none with serial numbers below 100, however-from its print runs for sale to collectors. One series sold by the bureau included "one $10 note from each of the 12 Federal Reserve Banks" with the lowest serial numbers available." The set went for $359.40.

The bureau also pitches its Lucky Money collection. One example is the bureau's $1 Fortune Notes, where "each uncirculated note has a serial number beginning with '8888' enclosed in an attractive folder festively adorned with Chinese art and symbolism." It aims to capitalize on the 8 being seen as a lucky number in Chinese culture. A single $1 bill in this series goes for $5.95, plus shipping and handling, though customers who buy in bulk can get volume discounts of up to $2 per note for 1,000 or more.

As the hobby has picked up attention in mainstream and niche media over the past year, the number of treasure-hunters with dollar signs in their eyes has grown.

While Mr. Futrell says he hasn't seen an increase in sales from this attention, he has seen a boom in requests for the value of bills. "What I have been is bombarded with questions asking about notes' values," he says, such as: "Is my note with 66632214 worth anything?"

To read the complete article, see:
These Collectors Hunt for Dollars With 'Fancy' Serial Numbers (www.wsj.com/articles/these-collectors-hunt-for-dollars-with-fancy-serial-numbers-1450147126)