I worked on this project from 2014 to 2015 (starting in my final year of school and finishing during my first year at university). The hardware is fairly standard for a nixie tube clock (arduino, DS1307 RTC, nixie tubes with driver ICs, high voltage supply module) but with the addition of a GPS module for precise timing synchronisation.
A screenshot of the schematic
Testing the nixie tubes before final assembly. The wire spaghetti is due to the fact that the PCBs are single layer through hole boards, photo etched at school since I did not have the tools (or money!) for SMD assembly at the time.
As of 2021 the clock is still working!