[C320-list] Second (hidden) HIN

[Mike Bird]

Every US vessel that needs a HIN must also have a second hidden HIN.
The primary HIN is on the transom or starboard side aft.  The
secondary can be hidden anywhere, even under a fixture.  The HIN
is not the same as the US documentation number.

   https://www.law.cornell.edu/cfr/text/33/181.29

Thanks to everyone who offered suggestions on and off list.  We'll
look again for the second hidden HIN next time we're aboard.

--Mike