His binary clock uses an Arduino Duemilanove (which fits perfectly in the tin) to keep time and control the indicator LEDs. The LEDs are arranged in two rows as you would expect, representing ...

His binary clock uses an Arduino Duemilanove (which fits perfectly in the tin) to keep time and control the indicator LEDs. The LEDs are arranged in two rows as you would expect, representing ...

From your 3rd-to-last picture (end view of arduino/board inside clock) you should have plenty of room for such a module. Something like a Chronodot or DS3231 module should work well.

Nixie tube clock build has been classed as an intermediate project and should take approximately eight hours to complete using an Arduino MKR WiFi 1010 microprocessor together with IN-1 Nixie ...