Ok, finally found a single tube 100 kHz. crystal oscillator that uses a neon
bulb relaxation oscillator that is synchronized to achieve 10 kHz signals.
The article appears in the fifth edition of Amateur Radio Techniques, on
page 287 and 288. It cites the original article from DL-QTC (August 1966).

The relaxations circuit is set up on the screen of the pentode oscillator,
which is also used as the feedback source for the crystal. So, it is used
apparently used as a synchronized 10 kHz source for the oscillator tube,
which is then operated as a mixer. So, we do not need the neon bulb to
operate at a high frequency.

73, Colin K7FM