North Vietnam, 3. Worker Congress, May 4th, 1962, Michel Nr. 214; A single stamp with a 12 xu nominal (standard domestic letter rate) was issued in perforation 11:0. 1,000,000 stamps were printed.
Here is the mint stamp.
Here is a rare single franking of this stamp on a letter mailed in early May to Klewitz in West Germany. The standard letter rate to West Germany was actually 50 xu but the sender duped the postal clerk to think the letter was going to “East Germany” by writing “Cong Hoa D.C. Duc” at the bottom of the address. A letter to East Germany only cost 12 xu so for the postal clerk the franking looked correct.
Similar single franking of the stamp but this time on a letter to the Soviet Union. Mailed in November of 1962. Moscow airport cachet in front. Moscow arrival cancel on the reverse.