For my reception report of Tokyo Coast Guard from Japan on 12577 kHz I received this nice QSL letter. I heard Tokyo Coast Guard with a DSC message as you might already have guessed.
I added two dollars to cover return postage. They were donated to the Blue Feather Donation as you can read in the letter. Two blue feathers accompanied the QSL: pretty cool!
Thanks to Hugo Matten who confirmed to use the address below:
Japan Coast Guard, 2-1-3, Kasumigaseki, Chiyoda-ku, Tokyo 100-8976, Japan