A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Robin Stuart
Date: 2019 Aug 1, 08:35 -0700
Thanks for the info. If the term was first used in the early 1900’s then it would have been at a time when the tricorne hat had long ago disappeared from daily fashion. The bicorne hat however was still in use in formal navy uniforms at the time suggesting that this might have been what is being referred to. On the other hand I have also seen the term “cocked hat” used in reference to coastal piloting where it could pre-date its use in connection with Sumner lines.
To clarify from my earlier post: the bicorne hat displayed in the Royal Navy Submarine Museum is actually labelled as a “Cocked Hat”. This the bicorne hat seems to be the default meaning in a naval context. Here are a few links
and Googling “national maritime museum cocked hat” turns up many examples,