++Update 1/11/2019** Added photos showing all four printed box designs and updated the Duet files to allow for a bit more clearance for the word cards.
Update 1/8/2019 I finally got around to designing the Codenames Duet Box and have uploaded to the list of files. Note that I am still waiting for my test print to complete so consider those files as "a work in progress" for a few days.
We now have four of the six Codenames games and the boxes take up a lot of storage space despite not having any real organizational storage inside (zip-lock bags do not count as storage...).
I designed up a storage box that can be used for two of the versions of the game (standard/original, and deep undercover). I also uploaded a case that should work for the Codenames Pictures. I am still working on the Marvel and Disney Editions.
The lid to the box is printed separate and then slid into the cover, and if you wish, glued into place. The tolerances for the cover and base are tight (.2-.3mm) to ensure the lid does not just slide off. Make sure your printer is calibrated and not over-extruding to a point where that clearance is affected. You can always sand the sides of the base to reduce friction and get a good fit.
Note I did not put storage for the small "hour-glass timer" in the original game as it causes a lot of wasted space in the design and we rarely use it when playing anyway.
Note The Deep Undercover version I received has a smaller card holder, but also has less word cards and the colored player cards are made of a thinner cardboard. As such, the small card holder actually slides in next to the word cads and prevents them from shuffling around too much. If enough people ask for or complain, I can tweak a version that is more tailored to that game (I really wish the producer would have a standard size and shape for their cards but it appears that each version of the game uses different materials and card sizes).
I printed the cover and insert with only 1 perimeter and 99% infill. This insures that there are no weird gaps in the corners and that the raised letters are totally filled. Make sure you print the cover piece with the lip (top) flat on the print bed to prevent need for supports.