I watched the 2012 movie adaptation of the 1947 documentary, Kon Tiki, made by Thor Heyerdahl of his famous balsa wood raft adventure from Peru to Polynesia. The movie was nominated for an academy award and it’s easy to see why. Very well done with some amazing special effects work. I had no idea that for the trip, Heyerdahl’s crew included not one but two radiomen! The film shows the radio receiver, key and headphones used. I wasn’t able to determine the receiver manufacturer, but it looks like they used a J-38 key. Power seems to have been provided by a crank-powered generator of some kind.
During the crossing the movie includes several scenes of the radiomen struggling to get antennas working. In one scene they attempt to get an aerial in the air with a balloon even. Ultimately they appear to have settled on a simple long wire hoisted up along the mast.
The radio is used to report their position during the journey and when they ultimately reach Polynesia you hear the sounds the the BBC coming from the radio and see one of the radiomen cranking the power generator.
It seems likely this would have been a QRP operation start to finish.
The movie is definitely worth watching. I caught it on Netflix.