I’m Kayla. I run a tiny coffee cart on weekends. I also help with school fundraisers and yard sales. Cash shows up. A lot. So I keep a counterfeit pen in my apron, right next to my Sharpie and a pack of gum. Sometimes I off-load leftover pastries or cart accessories through local classified sites, and if you’re thinking of doing the same you might appreciate this straightforward primer on Doublelist—it outlines the site’s safety tools and messaging filters so you can meet buyers with a bit more peace of mind. If your selling adventures ever drift south to Puerto Rico, you may need a platform that’s busy and hyper-local to the capital city—Backpage San Juan connects sellers with an active pool of San Juan buyers and includes location-based search filters so you can set up safe, in-person swaps without wasting time.
For anyone who wants the long-form breakdown, I published my take on the counterfeit currency pen I actually use with all the gritty details.
The one I use most is the Dri Mark Counterfeit Detector Pen. It’s cheap, small, and doesn’t scare people. It just looks like a normal marker. But it’s not. It’s a quick check that can save your cash box from a bad bill.
Here’s the thing—this pen is helpful. But it’s not magic. I learned that the easy way and the hard way.
Why I Bought It
I bought my first pen after a busy holiday craft fair. I got a big stack of $20s and one $100. My hands were cold. My brain was tired. I wanted a simple way to check bills fast.
A friend who works at a bank told me, “Use the pen, then use your eyes.” That stuck with me.
A while later, I chronicled the ups and downs of keeping that marker in my apron pocket all day in I carry a counterfeit currency marker—here’s how it really went.
How It Works (The Simple Version)
The pen leaves a mark. If the bill is on regular wood-based paper, the mark turns dark brown or black. If the bill is on real U.S. currency paper (cotton and linen), the mark stays light, kind of a pale yellow.
So:
- Light mark = likely okay
- Dark mark = likely suspect
It takes two or three seconds to show. I count “one… two…” then look.
Real Moments From My Cash Box
The Day It Saved Me
At a school bake sale, a guy handed me a crisp $100 for two brownies. That felt off. I ran the pen along the white border. Boom. The line turned dark, almost black. I smiled and said, “Do you have smaller bills?” He shrugged and pulled out two $20s. Those stayed pale. We moved on. No drama. Brownies sold.
The Day It Missed One
This part isn’t fun. At a flea market last summer, a woman paid me with a $50. The pen line stayed light. I thought, “Okay, fine.” Later, at the bank, the teller held the bill to the light and said the watermark didn’t match the portrait. No security thread either. My stomach dropped. The pen didn’t catch it because some fakes are made using real currency paper that’s been bleached. So the paper passes the pen test, but the other details don’t add up. That was a hard lesson, and I remember the buzz of the teller window and the hum of the coin counter while I stood there, annoyed at myself.
The whole episode felt like a rerun of another field test I shared in I tried a counterfeit bill pen—here’s what happened, complete with the same pit-in-the-stomach moment.
The Weird False Alarm
Once, a greasy, damp $10 from my coffee rush turned a little tan under the pen. I tried a dry corner of the bill. The mark stayed pale that time. I learned to test a clean, light area and give it a second try if the bill looks wet or grimy.
Small Habits That Help A Lot
I know, it sounds like a lot. But it’s quick. I run through these steps out of habit now:
- Use the pen on a light spot near the edge.
- Wait two seconds. No rush.
- Hold the bill up to the light. Look for the watermark that matches the portrait.
- Look for the thin security thread. It should run up and down, not across.
- Tilt the bill. The ink on the number (like the “100”) should shift color.
- Use your fingers. Real bills feel a little rough, like tiny raised lines.
Need a quick cheat sheet for those checkpoints? The U.S. Currency Education Program has a handy one-page reference you can print and keep by the register (download the Quick Glance Card).
On my cart, I keep a tiny UV keychain light. It’s not fancy. But it shows the security thread on newer notes. Handy when it’s dark out or my eyes are tired.
If you need a step-by-step visual, I lay these checkpoints out in how I spot a fake bill and the gear I actually use.
What I Like
- It’s fast. One swipe. Two seconds. Done.
- It’s cheap. I keep a spare in the cash tin.
- It’s not scary for customers. Looks like a normal marker. People don’t get tense.
- It pairs well with a light test. They work together.
What Bugs Me
- It can miss smart fakes, like bills made from bleached real notes.
- Wet or grimy bills can give odd marks. You may need a second try.
- The tip dries out if you forget the cap. Don’t be me. Cap it tight.
- It doesn’t help with foreign bills or plastic notes. Different game.
Real Use Cases That Made Me Keep It
- Soccer fundraiser: Ten people in a row paid with $20s. I checked each one. Light marks across the board. We kept the line moving, and parents liked seeing we cared.
- Yard sale morning rush: Someone tried a sketchy $20 for a box of old Wii games. Mark turned dark. I asked for a different bill, and they found one. No fight.
- Night market on a windy Friday: A $100 changed hands for a big coffee order and some croissants. Pen stayed pale, watermark matched, thread showed under UV. I felt safe taking it. We made rent that weekend.
That string of $20s also pushed me to get obsessive about that denomination—I learned to spot fake $20 bills the hard way, and the lessons still pay off every Saturday morning.
You know what? Those small wins matter. They keep stress low. They keep my cash box clean.
A Quick Word on Care
- Replace the pen every year or so. The ink gets weak.
- Keep the cap on tight, and avoid heat.
- Don’t press hard. A light swipe works best.
- Mark the date on the pen with a Sharpie so you remember when you opened it.
When the Pen Isn’t Enough
If someone hands you a big bill and something feels off—maybe the paper feels too smooth, or the colors look flat—slow down. Use the light. Ask for a smaller bill. It’s okay to set a store rule: no $100s after dark, or no large bills for small checks. I’ve done that at the cart after 8 p.m. It keeps things simple.
Also, I keep a note by the register: “We check cash for your safety and ours.” That small line helps. People get it.
For a concise expert rundown beyond the pen, the St. Louis Fed offers a quick read on four simple ways to spot counterfeit money (check out their guide).
For a clear, photo-heavy walkthrough of exactly what to look for, I like the free resources over at PrettyFakes.com.
Final Call: Worth It, With a Brain
Would I buy the Dri Mark Counterfeit Detector Pen again? Yep. I already have, twice. It’s a good tool. It’s fast. It catches bad paper. But it’s just one tool. Pair it with a light test, a quick tilt, and your fingers.
The pen is like a seatbelt. It helps most of the time. It won’t cover every crash. That’s why you still drive with your eyes open.
So yes—keep the pen in your apron, or your cash drawer, or your craft booth tin. Use it. Trust it for quick checks. And back it up with a look and a feel. Simple, steady, safe. That’s how I handle cash now.