Douglas RD “Dolphin” (1932)
Just wanted to mention a link I recently added to the “References” page. “Aircraft Used in Coast Guard Aviation” has photos and links to information about what appears to all the aircraft the Coast Guard has used throughout its history. This is a project of the Coast Guard Aviation Association.
They also have a chronological history, accounts of notable SAR cases, and a section called “In their own words” that includes historical narratives, hangar tales, and oral histories.
Chuck Hill's CG Blog 
The Grumman J2F-4 “Duck” which I think operated out of Greenland, and was able to carry up to 3 Survivors not including the Pilot. And was the USCG that operated from Greenland called the “North-South Polar, Inc.” to disguise their American identity from the Germans. Or were they a Separate entity operating independently…
There is an entry about the Duck. https://cgaviationhistory.org/aircraft_/grumman-jf-2-j2f-4-5-6-duck/
The US was quite open about taking over protection of Greenland after the Germans invaded Denmark.
Don’t think I ever heard of “North-South Polar, Inc”
We even wanted to buy Greenland after the war.
OK! The “North-South Polar” might just been a “Filler” in and otherwise By the Way Story, within the story…