I am sure we all have our favorite components we like to look for,
but crystals, crystal oscillators, and connectors are some of the best
treasures I look for when scrounging surplus circuit boards at a ham fest.

        There are some applications in which any clock from 1 to 10 MHZ
will do.  If there are any time-critical actions, just calculate according
to your clock.  Obviously, if one is going to write a magazine article and
produce a schematic for others to duplicate, then a standard frequency needs
to be used, but the main thing is that the frequency source be stable and
just about any crystal will do that.

Martin McCormick