Case

The 3D printed case can be found on Thingiverse.com.
https://www.thingiverse.com/thing:2790349
The Arduino Mega/TFT holder is called a "cradle". The Arduino/TFT modules slide into the cradle to make it easy to remove the arduino / RTC / TFT for programming.
Note that there is a holder for the RTC on the rear of the cradle.
The rear panel with buttons installed is designed to slide in and out of the case when needed. (See Photos)


This is a prototype of the completed case

And the rear


The top and rear panels are not fastened to the case. This lets you easily remove them so that you can work on the Arduino and clock modules. The bottom panel and cradle are epoxied to the side panels using 5 minute epoxy.