Bill Cornutt wrote:
>
> Is a box with a X in it the symbol for a crystal?

Allow me to throw in another letter....

On many schematics I've seen the letter 'Y' used to designate a
crystal.  The guts of a crystal is really a tuning fork - which
resembles a 'Y'.  Don't know if this is the reason, but it seems
logical.

--Matt