Mexican Army Decoder Disk | Historical Cipher Wheel

Write a note that only the right person can read. The Mexican Army Decoder Disk is a working wooden copy of the Mexican Army Cipher Disk, the five-disk cipher wheel used during the Mexican Revolution, and it turns every letter of a message into two-digit numbers. We make each one in our family workshop in Hudson, Florida (Creative Crafthouse has been making wooden puzzles and games since 2003).

Here is how it works. The bottom disk carries the alphabet, A to Z. Turn the four number disks above it to any position and leave them there: that setting is your key (the wheel has 456,976 of them), which you write down as the four numbers under A (for example A-07-46-53-84). To encode, find each letter on the outer ring and write any one of the 3 or 4 numbers in its column. Because the same letter can come out as a different number each time, the code holds up far better against letter-frequency guessing than an ordinary alphabet-shift wheel. To decode, set the same key, find each number and read the letter at the end of its column. The short video in the product photos shows a key being set and a word encoded.

Constitutionalist forces used this cipher during the Mexican Revolution, and in 1916 U.S. Army codebreakers read an intercepted message that had been sent with one. Our wheel follows the same five-disk layout, with the numbers 01 to 99 and 00 spread across the four inner disks, so you are working the same method its operators used. It is a historical cipher, so a patient codebreaker can still crack a long message by spotting patterns, and that is the idea behind the three challenge messages that come with it.

We cut the disks from MDF faced with real cherry veneer and laser engrave every letter and number, so the columns stay sharp and easy to read. The wheel is 5.75 inches across and 1 inch tall, a size that sits nicely on a desk or bookshelf between messages. Reviewers mention how smoothly the wheels turn, and one wrote that they "purchased two for my family, and we're keeping them as heirloom items."

In the box you get the assembled wheel, an instruction sheet with a worked example and three secret messages to crack without the key (hints, keys and answers are on the back if you get stuck), and a worksheet for writing your own messages. The wheel works with letters only, so spell out any numbers. One wheel both encodes and decodes, but whoever reads your note needs a wheel and your key too, which is why some customers buy a pair. We can also laser engrave a name or short message on the back when you order.

It makes a great Christmas or birthday gift for someone into history or secret codes, and it gives a teacher a hands-on way to show a class how a real military code worked and how it was broken. It also works well as a prop in escape rooms, geocaches and treasure hunts. If you would like a wheel that can send numbers too, the Janelle Cipher Wheel grew out of this cipher's design and adds digits and a few symbols. You can see the rest of our cipher wheels and Enigma machines here.

Add a personalized laser engraving to your puzzle or game.

• Perfect for gifts
• Business marketing opportunity