Etsy has some very cool retro designs using wood, Nixie tubes (or the Russian equivalents), LEDs, vacuum fluorescent and my favorite - 7 segment LED bars in Mason Jars made to look like giant Nixie tubes.
Some retro clocks use modern PICs with GPS time-setting, others dedicated 70s-era ICs or discrete logic. https://www.etsy.com/search?q=nixie%20clock
My focus for now will be to post vintage datasheets.
I find that the most obscure and seemingly worthless data sheets gets the most hits.
The first data sheet is the Cal-Tex Semiconductor CT7001: https://proaudiodesignforum.com/images/ ... ock_IC.pdf

Cal-Tex CT7001 Driving Sperry SP-151 Gas Discharge Display
Another relatively obscure Digital Clock IC is the American Micro-Systems AMI S1736 designed for liquid crystal displays.
AMI S1736 Digital Clock IC data sheet: https://proaudiodesignforum.com/images/ ... C_1972.pdf
An earlier copy of the data sheet included the internal logic diagram of the AMI S1736.
It's not often you see a gate level internal logic diagram...

AMI S1736 Digital Clock IC Internal Logic Diagram
AMI S1736 Logic Diagram in large format: https://proaudiodesignforum.com/images/ ... iagram.jpg
LCDs at the time were very expensive.
My brother designed and sold a clock using the S1736 that drove the Fuji Minitron 3015F incandescent displays.

KA Electronics "Time Machine" Digital Clock Kit Circa 1972 Using the AMI S1736 and Fuji Minitron Displays
Going through some old parts I hadn't touched since 1975 I recently discovered that my brother Byron had AMI brand his clock ICs with the KA logo and an "in-house" part number the "KAS1013."

KA Electronics-branded AMI S1736 Digital Clock IC
The schematic for the KA Electronics clock showing the AMI S1736 interfaced to Minitron displays is here:
https://proaudiodesignforum.com/images/ ... n_1972.pdf
My Heathkit clock uses gas discharge displays from Sperry.

Heathkit GC-1092A Digital Clock Schematic Using the Mostek MK5017 and Sperry SP-352
Large Heathkit GC-1092A DIgital Clock Schematic: https://proaudiodesignforum.com/images/ ... -1092A.jpg

Sperry SP-152 SP-352 SP-332 Gas Discharge Displays
I scanned this Sperry Information Displays Clock Display Catalog from 1973.
It's got pin outs for the SP-151, SP-152, SP-332 and SP-352 display modules.
https://proaudiodesignforum.com/images/ ... g_1973.pdf
Sperry also published several Digital Clock Application Circuits:
https://proaudiodesignforum.com/images/ ... s_1973.pdf
SP-151 MM5311 Interface
SP-151 MK-5017 Interface
SP-352 MK-5017 Interface
SP-151 AMI SP1736 Interface
SP-151 MK5017 Automatic Dimming
SP-151 AM/PM Drive
SP-151 MM5314N Interface
Power supplies
SP-151 MM5370 Interface (Preliminary)
The Mostek MK50250 Clock IC

Mostek MK50250 Digital Clock Application Circuit Driving A Common Cathode LED Display
Mostek MK50250 Data Sheet: https://proaudiodesignforum.com/images/ ... _Clock.pdf
An Aircraft Digital Cabin Clock using the MM5314

An Aircraft Digital Cabin Clock using the MM5314, Byron Kirkwood, Kirkwood Associates, March 1973.
An Aircraft Digital Cabin Clock using the MM5314 pdf: https://proaudiodesignforum.com/images/ ... d_1973.pdf