Just like most other countries, you don't want to get stuck holding the bag on a bad currency note. Knowing how to quickly identify the security features of the Mexican peso can protect you from getting passed a bum bill.

Mexican Pesos from $20 pesos to the $1000 pesos note have several distinct characteristics to help you to identify genuine & counterfeit Mexican pesos. Tourists and North Americans who visit and even those that live here year round can often be easy marks for receiving short change and counterfeit pesos.

This article is compiled directly from the Bank of Mexico's page on how to identify the security measures invalid Mexican pesos. Unlike the United States, Mexico issues its own currency and the money is the property of the country of Mexico. Mexico does not borrow its money from a federal reserve bank.

I suggest if you have some Mexican pesos in your possession, take a few out and identify the security features on a bill in your hands. Once familiar with these markings you can very quickly assess the validity of notes passed to you. And purely by statistics, a few of you reading this article are going to discover some bad bills – first hand.

The Security Features of the Mexican Peso

Give it the old Touchy-Feely

There, now that you know your Mexican peso notes, let's determine how to tell the good ones from the bad ones.

The first line of defense for any monetary system is to make forgery more expensive than earning the money legitimately, and that begins with the print stock. All of the current Mexican notes are printed on a polymer paper stock blend that feels plastic like. Some of the new $20, $50 and $100 peso notes are on an entirely plastic stock.

Compare a peso to a sheet of common paper and you can tell a photocopy forgery in a spilt-second. Color photocopies make up a significant portion of the lazy man's counterfeiting. But by testing the note between your fingers for that slick feel, raised thermographic type and consistent texture, you can protect yourself from the lowest level of counterfeiting very easily.

Perfect Registration

The second tier of protection comes from the technology and skill of the money printers. Registration from one side of the note to the other can provide a quick check when holding the note up to the light. Each denomination has a fractured map of Mexico and a compass rose printed, 1/2 on each side of the note. When held up to the light the map and compass rose become complete.

The "Secret" Watermark

The third tier defense is printed right into the substrata of the note's paper and is very difficult for counterfeiters to emulate successfully. On the diagram to the right, the full image of each denomination has a red box, when held up to the light a ghosted repetition of the featured face can be seen, larger denominations also have the note's value in the watermark. The image is nearly invisible under normal lighting.

Through the Window

Smaller denomination notes also have a clear plastic window molded right into the polymer substrata. You should not be able to separate the window from the note with your fingernail. Printed into the window is a holographic design, as the note gets older these can be hard to discern. The different shape and position of the window were supposed to allow vending machines to identify note values easily.

Security Thread and RF Reflector

In the newest series of notes, it is said that the security thread is also a passive radio frequency reflector. When exposed to a specific frequency of radio waves the notes respond with a harmonic frequency. When a significant reflection is received the authorities know a large amount of cash is present. Eventually, this will be used to detect large amounts of undeclared/untaxed cash transiting borders, as it is currently used in the United States. The new Mexican border crossing at Tijuana has been equipped with this detection technology, along with several point-of-entry airports in Mexico.

The thread also allows certain commercial counting machines to detect individual bad bills and alert an operator quickly and accurately.

3D Double Sided Security Bar

The larger notes have a security thread printed from one side to the other of the note. Also in perfect registration, the security thread when held up to the light, appears perfectly complete.

This thread is part of the paper from its manufacture. It has protruding parts where you can see the figure of a snail prehispanic related to the god of the wind, Ehécatl. When the note is turned from front to back, the snail moves from left to right and when the note is rotated from left to right, the snail moves up and down. That is, it moves opposite to the movement of the note.

Color Changing Inks

Mexican currency is also imprinted with a holographic thermography which changes color when the note is angled. Shown right are the various color change makes on each denomination of the note. Along with the plastic windows on the smaller notes, I found this security feature waned as the note became old and tired, on new notes, the effect is quite pronounced. The small red box on the full notes shown right indicates the location of the special markings. The divided image is slightly raised and will change color as the note is angled left to right.

Micro Printing

The final security measure on Mexican pesos is the most difficult for counterfeiters to recreate. Microprinting is so small that lesser papers and lesser inks on a copier or regular printing press would run together in an indiscernible blob. Unless your eyes are very good or very young, it is difficult to even see the micro printing without a magnifying glass or loop. The microprinting is also done in colored layers, all tactics to make the money more difficult to print that to earn. The text also decreases in size line by line.

Black Light Analysis

The papers and inks of the notes are designed to reflect a pattern when exposed to ultra violet light. But since few of us carry a black light in our back pocket, we'll let those security descriptions await you on the Bank of Mexico website.

As a final note, I will suggest that it is important to know your own national currency as well. Counterfeit. dollars and loonies can also be found a tourist locations around the world. So know your money!

Editor's Note: Any hidden references in Mexican currency to Pink Floyd's 'Dark Side of the Moon' are purely coincidental.