I can't provide many further details because the circuit is commercial IP and I don't have the software.
All I can say is that it has an Atmel microcontroller, a keypad, rotor and backlit LCD. Pretty simple.
The "light bulb over the head" idea was realising the front panels could be modified to program other panels. We got a ready-made board, keypad, display and case. We often had spare panels that were no longer saleable as new but working perfectly otherwise. So it used stuff that would have been e-waste.