Mail between China and Korea after 1945 was not common, therefore it was difficult for collectors to get hold of such covers. Business contacts did not yet exist; the missionaries were paralyzed by war and civil wars and they lacked support from their home countries. It is probably no coincidence that the letter shown below comes from US sources and was sent to the YMCA (YMCA).
The letter went through the censorship procedures. The slightly chipped purple box cachet on the front of the letter is probably a censorship notice. There are similar registered boxed cachets, but the letter is not registered, because the postage in the amount of $ 170,000 CNC corresponds exactly to the postage for an international airmail letter of the first weight level on the date of dispatch, July 5, 1948. That “RELEASED BY CENSORSHIP” is a US censorship cachet.