North Vietnam, Reptiles, February 25th, 1966, Michel Nr. 432-437; Six stamps with the nominals of 12 xu (four stamps), 20 xu and 40 xu were issued perforated 12.5 and imperforate.
Here is the mint imperforate set:
Here is a rare letter featuring the entire im-perforated reptile set on an express mail cover to Klewitz from November of 1966. Im-perforated stamps on postally used cover are very rare. The letter has an overall franking of 1.32 Dong which covered the standard letter rate of 50 xu plus the express mail fee of 50 xu. Given the higher postage ad the fact that Klewitz rarely ever wasted any postage, the letter must have exceeded the 20 gram base tariff.
Registration Nr. 101280