Ever wonder if that Benjamin Franklin in your wallet could be worth serious money? Turns out some $100 bills are worth way more than face value — and I'm talking millions.

So here's the thing about Ben Franklin on the $100 bill. When the Federal Reserve first issued these notes back in 1914, they started featuring his portrait, and it's been the standard ever since. But before that, you had all kinds of different designs on the C-note. That's where collectors go crazy.

Take the 1863 $100 Gold Certificate. This thing is absolutely legendary. Only three are known to exist, and two sit in the Smithsonian. The one in private hands? It sold for $2.115 million back in 2013. These weren't just regular bills — they literally said "One Hundred Dollars in Gold Coin" on the back.

Then there's the 1882 version featuring Thomas Hart Benton. Started at $253,000 in 1998, but by 2014 it was pulling over $822,500 at Heritage Auctions. Same story — only three known examples floating around.

The 1878 Silver Certificate is another beast. Not a single one was publicly shown for 30 years until 2019, and when one finally hit auction that year? $540,000. Only five exist, and some are literally lost to history.

But here's my favorite — the so-called "Watermelon" $100 from 1890. The name comes from the zeros on the back looking like watermelons. Only 35 known examples, and they've been pulling serious money. One sold for $356,500 in 2005.

Now, most of these insane prices are for pre-1914 stuff before Ben Franklin took over. But don't sleep on modern bills either. The real money in newer currency is all about fancy serial numbers. I've seen 2017 $100 bills listed for nearly $1,000 just because the serial number is a palindrome like 44799744.

The really rare ones — like 00000001 or perfect sequences like 87654321 — those can hit $15,000. People collect solids like 88888888, super repeaters like 36363636, radars, double quads, all that stuff. It's a whole market.

So next time you're looking at a Ben Franklin bill, check that serial number. Might just have something worth holding onto.