You'll need the original Cryptex files from pbloom's http://www.thingiverse.com/thing:7233

The OpenSCAD file can be used to generate any of the 36 letters or numbers on the cryptex. The OpenSCAD file works by splitting the interior and exterior into separate pieces, rotating the exterior until it aligns the notch with a new letter, and then joins the two pieces back. Also, it appeared that the original STL was saved in inches, rather than mm, so I scaled the file up by a factor of 25.4.

As an example, although pbloom only uploaded the letters "DEC14", I've included the ring for the letter "Z" made with this OpenSCAD file. I've also included a key of how much the outer ring should be rotated to match with each letter and number.

1. Use the legend in the OpenSCAD file to get the letter you want
2. Export desired letter/ring combination