First the letter was posted from Reykjavik, Iceland to Moscow. Then the letter was delivered to the ISS by the Russian "Progress MS-08” supply spacecraft. To document the delivery, on board the station the letter was marked with all proper board seals including the Russian official “Russian Post. ISS. Russian Segment” round board post mark dated February 15, 2018, the day when the “Progress MS-08” spacecraft docked with the ISS.