Los 6308
POSTAGE-FREE OFFICIAL LETTERS OF THE LATVIAN POSTAL SERVICE: Sovjet postal stationery envelope disguised and used in Widrisch as registered cover, for sending in to the main post office in Riga the main portions of money transfers paid out), scarce
Reference: "Lettland vor dem und als Teil vom Generalkommissariat OSTLAND", page 119, Harry von Hofmann (2001)