North Vietnam, 20. Anniversary of the 1946 Elections, January 6th, 1966, Michel Nr. 424; A single stamp with a 12 xu nominal and perforated 11.0 was issued.
This is the mint stamp.
This stamp was not officially released imperforate however a small number of imperforate trial proofs have come to market. Here is one of them.
Rare single franking of the 12xu stamp on a letter (full contents preserved) sent from Hanoi to Czechoslovakia in 1966.
Rare express mail letter to Klewitz with a single of the stamps from September of 1974. At 3.34 Dong the letter is most likely over-franked. A standard registered express mail letter only required 1.60 Dong. Nevertheless, rare postal usage of the high 3 Dong value from 1961.
Here is a registered letter sent to Klewitz in April of 1966 carrying one of the 12 xu stamps. The mixed currency franking amounted to 1.15 Dong (the 50 Old Dong stamps the back was worth 5 xu in 1966) which was a tad above the required standard registered letter postage of 1.10 Dong.
Registration Nr. 101260