dave wrote:
You can pick whatever number you want for a Vanity callsign.

It's not a ham call. It's an experimental radio license (according to the
FCC):

WE2XGR WARREN H. ZIEGLER 0151-EX-PL-2007 New experimental to operate
in 505-510 kHz and 510-515 kHz for propagation studies and research of
LF communications systems.

The 6 means something else than what you thought, probably that this is
beacon number 6.

Usually stations of this type operate in several locations on a rotating
schedule.

Look up the 14.1 mHz beacon system. They operate across the world on a
rotating basis, with various power levels.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM