I have a few nixie clocks around here, though only one of them is currently working (and that's after several surgical operations). Here's the one which runs, which was offered as a kit by "B&F Enterprises" in the early '70s, based around
74xx-series TTL ICs. Whoever built it didn't do a great job, and I don't think the design was too great to begin with, but it's running quite well now. ***KNOCK ON WOOD***
Here's one of my project clocks, a homebrew of some sort from the '70s. Again, it uses TTL ICs, though
mounted in perfboard and
hand-wired. Unfortunately, someone stole the power transformer out of it at some point, so I have yet to test it.
I have several
Heathkit clocks which technically don't use nixie tubes, but they use
Sperry "Panaplex" digits which give a similar effect in 7-segment form. Similarly, I have several
Numitron tubes which I'm planning to use to build a
clock. Getting back on-topic, I also have some pieces of test equipment which uses nixie tubes, like a
Hewlett-Packard 5245L frequency counter (which I'll likely keep as-is), and an Acton Labs 330A "Digital Phasemeter", which I'm considering turning into a clock.