Last year this cover was for sale on Ebay. I didn’t buy it, but was intrigued by it. The original reason to be interested was because of the seal on the back. This turned out to be an American anti-polio Easter seal, which just like the Korean anti-tuberculosis Christmas seals were sold to raise money to fight a disease, in this particular case polio, a terrible decease which was then still quite common everywhere. But it turns out the front of the cover shows something about Korean history I had never heard of before: how one ship provided electricity to a large part of South Korea.
The cover was sent by Arthur Spooner who worked on board a ship named “Jacona”. That ship has its own lemma on Wikipedia: “SS Jacona was the first floating electric power plant. This powership was a cargo ship converted to a mobile electric generator plant for emergencies. It was used by the United States Navy during World War II and supplied electric power to South Korea on a temporary basis.”