Introduction: Detecting Counterfeit Currency, US Dollars.

by tonytran2015 (Melbourne, Australia).

When traveling oversea you may have to use US currency. However, this currency is the target of many counterfeiters and if you are unfamiliar with it and cannot distinguish between real money and counterfeit money you may suffer substantial loss. Counterfeit notes are not rare in South East Asia.

This posting shows the most effective ways to distinguish between real and counterfeit money. You need no tool for most of these tests but you may need to carry a genuine $5US note with you all the time as your sample (a smaller note of $1US may do).

The tools for some of the tests are: A LED torch, a fridge magnet and a high power (x10) magnifying glass.

Step 1: 1. Security Band Using Hologram.

Figure 1: Composite photos of a stretched out $100US note. The "stretched dollar" has four blue security bands instead of one. Each band is the picture of the same physical band on that dollar note viewed from a different angle. Figure 2: Composite photos of the magnified views of one same blue security band. The security band is a hologram feature on the $100US note. The checker pattern on the blue security band moves smoothly downward when the viewing angle changes from left to right.

The new 100 US dollar notes have beautiful blue hologram bands with tiny pictures of the number 100 in checker pattern. When the viewed at varying angle from left to right these patterns smoothly move downward as if they float on the notes.

Step 2: 2. Iridescent Ink for Features.

Figure 1: An $100 US note, with its colour changing "bell in a bottle". It is shone by a strong light beam at normal angle (top picture) then at glancing angle (bottom picture). The change in colour (from bronze to green) on the $100US note is obvious.

Featured marks by iridescent ink which changes colour when view from different angles: On the $100 US note, the picture of a bell in a bottle can be made to change from bronze to green by shining a strong light beam at normal and at glancing angle.

The test is easy when you have a LED torch to shine a strong light beam onto the ink and change the beam angle from normal to glancing.


A LED torch is helpful but not essential.

Step 3: 3. Hidden Figure.

Figure 1: When view against a strong background light, a hidden image is shown, matching the printed portrait on the note.
When view against a strong background light, a hidden image is shown, MATCHING the printed portrait on the note. ===> This is a strong test against counterfeit notes.


Counterfeiters have been known to reprint high value notes on base material of lower value notes to keep hidden figure and to fool iodine pens. It is vital to have hidden figures matching the printed portrait [1], [2].

Step 4: 4. Hidden Small Print Instead of Security Wire

Figure 1: Small print is hidden inside the base material. It is seen when the note is hold up against a strong background light.

Small print buried inside the base material now replaces the old metallic wire buried inside the base material. It is seen when the note is hold up against a strong background light.

Step 5: 5. Magnetic Ink.

Figure 1: The ink on the genuine note is magnetic and is clearly seen attracted by a fridge magnet.

When holding the rectangular note vertically by grabbing its upper short side, you can easily see that the ink on the US dollar notes is attracted by a fridge magnet hold in the other hand.


You need a ceramic fridge magnet for this test.

Step 6: Your High Power Magnifying Glass Is a Useful Anti-counterfeit Tool.

Figure 1, 2: A high power (×10) magnifying glass (disassembled in the second picture) is required for inspecting fine details on currency notes.

CLEAR and CRISP printing is the common feature of most currency notes in the world. Currency issuers use their best printing technology to stay ahead of counterfeiters. They design their currency with very fine details such that only their genuine notes can have the details (for example, watermarks on the base) printed clearly.

You certainly need a good high power (x10) magnifying glass to check the printings. A quality high power magnifying glass has 3 lenses glued together as in the second figure.

Step 7: 6. Fine Printing.

Figure 1: The treasury seal with fine clear and crisp printing. Near to it is the fine character line bordering the unprinted area reserved for the hidden figure. Figure 2: Finest letters on a $100 US note.

The fine printing of letters of height of 0.5mm (or 1/50inch) in bronze colour is found on $100 US note on the curved character line bordering the unprinted area reserved for the hidden figure. It is near the green treasury seal.

The finest printing on US dollar notes is in black letters of height of 0.2mm (or 1/128 inch). It is placed at different places for different denominations. They are:

a/- at the bottom edge under the name Franklin for the portrait on any $100 US note ,

b/- following the denomination number 20 on the left side of the name Jackson for the portrait on any $20 US note,

c/- on top of the name Hamilton for the portrait on any $10 US note.

d/- inside the decorative loops at both ends of any $5 US note.

e/- the words E.PLURIBUS UNUM of a height of 0.3mm on top of the wings of the eagle in the National Seal at the back of any $1 US note.

===> You need to be familiar with these printings to check their quality.


1. 10X magnifying glass.

2. You need to carry a $5US note with you all the time to make non-arguable judgment on the print quality of notes

Step 8: 7. Blue and Red Fibers in Cloth Base Material.

Figure 1: There are many blue fibers in the base material. One red fiber is seen in the center of the figure. Figure 2: A raised weave pattern is seen on the surface of the note.

The base material is made of cloth and is not paper. Under the magnifying glass it has the structure a white wool blanket. There are occasional blue and red fibers mixed into this white base material. There are less red fibers than blue fibers.

Any note of $5 or more has weaving patterns on most of its surface.

1. 10X magnifying glass.

Step 9: Effective Detection Strategy.

The seven tests have been given are in order of increasing difficulty. They are thus in the right order for an effective detection strategy. From my searches using the Internet, I have not found any case of counterfeit US dollars passing more than four of these seven tests.


1. Iodine pens give yellow ink mark which darkens to brown on contact with starch from ordinary paper. These pens are sold to detect fake US dollars. Counterfeiters have been known to waterproof their counterfeit notes to fool these pens. They have also been known to reprint high value notes on lower value notes to fool those pens and to keep the hidden figure.

2. There are also UV torches sold to detect counterfeit currencies of other countries. Every $5 or $20 US notes has a full length vertical UV fluorescent line but this feature is hard to excite on other US notes. High quality UV lights are required for this anti-counterfeit feature on new US notes. A high quality UV light source has UV of short wavelength and narrow spectrum with little visible light emitted. It is neither small nor cheap.

Step 10: Reducing Exposure to Counterfeit Currency.

When traveling and using unfamiliar currency you can reduce your risk to counterfeit currency by adopting these cautionary rules:

1. Carry a variety of high value notes so that you can combine them to pay each of the purchase charges without receiving any change in high value notes.

2. Only receive high value currency notes from registered banks (They are obliged to check currency notes when receiving and give you genuine usable notes).

3. Ask the banks to give you the combinations suitable for your trip until your next bank visit.


[1]. gila lunatic, How to make counterfeit 100 dollars, lunaticg, , accessed 22/7 2016.

===> Its title is sarcastic. The article does NOT help counterfeiters.

[2]. Unknown Author retired from youtube as of summer 2011, A lesson in printing fake money, CK-World Online Tech Videos on Youtube, , Uploaded on Apr 26, 2010, accessed 22/7 2016.

===> Its title is sarcastic.. The article does NOT help counterfeiters.