You probably don’t look at your cash. Not really. Most of us just swipe a card or tap a phone anyway, but when a crisp C-note hits your palm, the instinct is to check for the watermark and shove it in your pocket. That's a mistake. A massive, potentially expensive mistake.
While most money is just... money, rare 100 dollar bills are basically lottery tickets hiding in plain sight. We aren't just talking about old dusty notes from the 1800s that your great-grandpa left in a cigar box. Some of these are modern notes with tiny, "blink-and-you-miss-it" printing errors or specific serial numbers that collectors—the kind with very deep pockets—will fight over in auction houses like Heritage Auctions or Stack’s Bowers. Honestly, the difference between $100 and $10,000 can be a single misplaced digit or a slightly off-center seal.
The obsession with "Fancy" Serial Numbers
Look at the green numbers. Every single bill has a unique serial. Most are boring. But collectors have a thing for "Fancy Serials."
If you find a Low Serial Number, like 00000001, you’ve hit the jackpot. For the Series 2002 or 2009 notes, a number 1 serial can fetch anywhere from $10,000 to $20,000 depending on the condition. Even something under 100 is worth a massive premium. Then there are "Ladders." A perfect ladder is 12345678. They are incredibly rare. Most "ladders" people find are actually "broken ladders" (like 00123400), which are cool but don't command the same crazy prices.
Binary bills are another big one. These only use two digits, like 88080880. Why do people care? Humans love patterns. It’s that simple. A "Super Radar" note—where the serial number reads the same forwards and backwards and the interior digits are all the same except the ends—is the kind of thing that makes a paper money geek's heart skip a beat.
The 2006A "Mismatched" Error
Errors are where the real money is. The Bureau of Engraving and Printing (BEP) is usually terrifyingly efficient, but they’re still human. Sorta.
In the Series 2006A $100 notes, a famous error occurred where the serial numbers on the left and right sides of the bill don't match. This isn't supposed to happen. Ever. The computer systems are designed to catch this, but a few escaped into the wild. If you have a bill where the left serial ends in a 4 and the right ends in a 5, you aren't looking at a counterfeit. You’re looking at a four-figure payday.
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Does the "Series" actually matter?
People always ask about the year. On a $100 bill, the "Series" year is tucked next to the portrait. It doesn't actually mean the year it was printed; it means the year the design was adopted or a new Secretary of the Treasury took office.
1928 is a big one. This was the first year of the "small-size" notes we use today. Before that, US currency was "Large Size"—literally nicknamed "horse blankets" because they were so big. A 1928 Gold Certificate $100 (with the bright orange seal and serial numbers) is a grail item. These were used back when you could actually trade your paper for physical gold. In 1933, FDR made it illegal to own most gold, and these notes were supposed to be turned in. Finding one in a drawer today is like finding a piece of outlawed history.
The "Star Note" mystery
Ever see a little star instead of a letter at the end of the serial number?
That's a replacement note. When the BEP ruins a sheet of bills during printing, they can’t just print the same serial numbers again—that would mess up the accounting. So, they swap in a "Star Note."
Are all Star Notes rare? No. Most aren't.
To know if your Star Note is actually one of the rare 100 dollar bills collectors want, you have to look at the "run size." If the BEP only printed a run of 320,000 star notes for that specific series and district, it’s rare. If they printed 3.2 million, it’s just a hundred bucks. You can check these on "Star Note Lookup" sites that track production totals from the Treasury.
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Condition is everything (Don't iron your money!)
I've seen people try to "fix" their old bills. They use an iron to get the creases out or—heaven forbid—lightly wash them.
Stop.
In the world of numismatics, a "processed" bill is a ruined bill. Collectors want original paper crispness. They want "embossing," which is the slight raised texture you feel when the ink is pressed into the paper. If you iron it, you flatten that texture and kill the value.
The grading scale goes from 1 to 70. A "Choice Uncirculated 64" bill might be worth $200, but the exact same bill at a "Superb Gem Uncirculated 67" could be worth $1,000. It’s that tight. If you think you have something special, put it in a PVC-free plastic sleeve immediately. Your finger oils are actually acidic and will yellow the paper over time.
The 1990 "Error" that wasn't
There's a persistent myth about the 1990 series. People think because it was the first year they added the security thread and microprinting, that there are "missing thread" errors worth millions.
Usually, the thread is just buried deep in the paper or it's a counterfeit. Real "no thread" errors exist, but they are verified by light tests. Don't believe every TikTok "expert" claiming their 1990 Benjamin is worth a house.
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Gold Certificates and Red Seals
Before the Federal Reserve took over everything, we had different types of currency.
- Gold Certificates (Orange/Yellow Seals): As mentioned, these are high-value.
- Silver Certificates (Blue Seals): These were mostly $1 and $5 bills, but $100s exist from older series.
- United States Notes (Red Seals): These were issued directly by the Treasury. A 1966 $100 Red Seal is a very popular collector's item because it was the only year the $100 was issued as a "Legal Tender" note with that red ink.
How to spot a fake while looking for a rarity
When you’re hunting for rare 100 dollar bills, you’ll find fakes. It’s inevitable.
The best way to tell? The portrait. On a real bill, Benjamin Franklin looks lifelike. His eyes have depth. On a fake, he often looks "flat" or muddy.
Check the "color-shifting ink" on the bottom right "100." On modern notes (Series 1996 and later), it should change from green to black or copper to green when you tilt it. If it doesn't shift, it’s just glittery paint, and your bill is worth zero.
Actionable Steps for the Aspiring Collector
If you want to actually make money finding these, you need a system. You aren't going to find a 1928 Gold Certificate in your change from Starbucks. Those days are over.
But you can find modern errors and fancy serials.
- The Bank Strategy: Go to your local branch and ask to withdraw $1,000 in hundred-dollar bills. Tell them you want "older styles" if they have them. Most tellers don't care.
- The "Bace" Check: Quickly scan the serial numbers for repeating digits (7777), sequences (1234), or low numbers (under 1000).
- The Light Test: Hold every bill up to a light. Look for the "mismatched serial" error or "double watermarks."
- Reference the "Greensheet": This is the professional price guide for paper money. If you find something weird, don't guess the price. Look it up or check "Sold" listings on eBay to see what people actually paid—not what sellers are asking.
- Get it Certified: If you find a bill that looks like it's worth more than $500, send it to PMG (Paper Money Guaranty) or PCGS. Having a professional third party grade and "slab" the bill in plastic is the only way to get top dollar when you sell.
Searching through cash is a volume game. You might look at 5,000 bills and find nothing. Or, you might look at one and find a 1966 Red Seal that pays for your next vacation. Just keep your eyes on the serials and keep the paper crisp.