This is a copy of this Nixie tube clock that was published in the December 1970 and January 1971 issues of Popular Electronics.
Here are new schematics and PCB layouts
Here is the reproduction with six digits installed.
Here is a prototype cover
Earlier version with just 2 digits, power supply wiring has been moved under the boards.
Here are some more photos from the magazines.
6 Digit version
4 Digit version