The 1939 Soviet census, conducted from January 17 to January 26, succeeded the 1937 Soviet census that was declared invalid. It happened only two years after the previous census, due to the failure of
USSR reverse of a January 23rd, 1939 registered cover sent in Leningrad. The text translates as: '17 January 1939, start of the All-Union Census. Citizen! Do not forget to go through the census.'