Here's an example of a transistor based SCR oscillator clock
Example 1 - "Alan Yates"
Example 2 - "Electronic Circuits Manual pg. 171"
Example 3 (non working) - Electronic Counting Circuits (Mullard) pg.50
Explorations in transistor based SCR ring counter circuits.
Charest's clock is impressive due to the physical layout, thanks for pointing it out. It would make a kid vow to take up engineering. Nixies would be the ideal display except that they are so expensive. Alternatively maybe a ring layout simulating an analogue clock.