I chose a generic hinge case as the basis for the model as it's dimensions closely matched that of the Trezor device. I unfortunately didn't bookmark that file but if I do find it again I'll link that base case here. Dimensions have been altered slightly and cable clips added to the lid to secure the Trezor data cable. A Trezor Safe 3 insert has been generated which is a snug to the Trezor so retains the unit but it is not an overly tight fit leaving it an easy task to remove.  The insert is a tight fit into the case so there is no possibility of removal without damaging or destroying the case. This means coded information can be 3D printed onto the lower case face or the lower insert face to aid access or wallet recovery.

The case is printed in lower and upper sections and snap together with a fair bit of upward force. You won't get them to mate from the side, one body hinge needs to be snapped down onto and into the other. The coupled hinge provides decent friction so stays where it is opened.

I printed my case on a textured plate, it can be printed on a smooth plate if a smooth base and lid finish is preferred. Parameters for a PLA print were 0.1mm layer no supports. I have added text to my own storage case insert to identify which wallet has been allocated to the particular Trezor device stored within the box.

The choice of filament may improve the model. The clips can be snapped in PLA if you get too forceful. Possibly a PET print would be more suitable for improved flexibility but I only have PLA so that is what I used.