[time-nuts] Are there SC-crystals out there in the wild that are not Overtone?

[Richard (Rick) Karlquist]

> 
> I seem to recall that crystals for frequency control (on a commercial 
> basis) were sort of a post WW2 thing (partly because of developments in 
> piezo hydrophones for sonar)
> 

Crystals for radios were well established pre-WWII.  There was an
FCS paper ~30 years ago about the WWII quartz shortage and the
research to find alternatives to quartz (which they didn't know
how to grow synthetically yet).  Spoiler alert:  there is nothing
else like quartz!.

Novice hams routinely used war surplus crystals (FT-243?) after the war.
I had some at 3.7 and 7.15 MHz fundamental and they oscillated
fine with receiving tubes, circa 1965.

There was some standard military crystal test set from the war that
was always referenced in crystal specs in those days.  The test
set was in essence a "golden" oscillator.

Rick N6RK