I built this clock over a decade ago. Although it was built around 2006 most parts have date codes from the 1960’s and 70’s to keep it as accurate to the period as I could. Unlike many of the NIXIE clocks you see today that use a modern micro-controller this clock uses TTL logic. Each NIXIE tube has it’s own driver IC (the NIXIEs are not multiplexed) and it’s own divider stage. It uses the 60hz line frequency here in North America as the time base. It’s simple, some of the design is brute force however it got the job done.