Tim Walker sent me a link to his great Scope/CRT clock build.  The internal mechanism is based off Thiem-Work kit.  He used a DG 7-16 display and the enclosure is made out of a clear plexiglass.  One other feature that he included that I haven't seen before is the inclusion of a motion sensor that only displays the time when motion is detected.  That has to be one of the most elegant burn-in protection mechanisms I've seen.

Lastly, be sure to check out his neon work at http://timwalker.cc/.  He has a lot of cool stuff to show off.

http://timwalker.cc/scope/scope_clock/Scope_Clock_Project.html