It is an organizer to hold Magnetic Card Wallets, Extra ROM Modules or slot covers, and a place to hold a Card Reader when not mounted on the Calculator.
The STL File is available at:
https://www.thingiverse.com/thing:3851041
or
https://www.prusaprinters.org/prints/5509-hp-41-accessory-organizer
Happy Printing...
![Smile :)](./images/smilies/icon_e_smile.gif)