North Vietnam, 15 Years Peoples Army, December 22nd, 1959, Michel Nr. 113; A single stamp commemorating the 15th anniversary of the Vietnamese Peoples Army was issue to cover the standard domestic letter rate. Perforation was 11:0. Here is the official Xunhasaba stamp bulletin that was released upon issuance of the stamp.
Air mail letter mailed in April of 1960 from Hai Phong to Czechoslovakia using one of the 12xu People Spirts and one 12 xu Peoples Army stamps for an overall postage of 24xu. The standard letter tariff to Eastern countries amounted to 20xu until March 1st, 1960 when it was reduced to 20xu. So, it appears that this letter was of the second weight level.
Letter with a mixed franking of four 12xu stamps (including one of the Peoples Army stamps) for an overall postage of 48xu sent in June of 1960 from Yen-Bai to East Germany. The letter was addressed to a fellow Vietnamese in a local engineering school. Unusual small post office cancel in Tran-Yen.
Postally used letters with the stamp are rare. Here is one example that was sent to Theo Klewitz on December 22nd, 1959. It carries an interesting mixed currency franking. The 12 Year Republic stamp of 20 Old Dong from 1957 was worth only 20 xu in 1959 so the letter was overall franked with 38 xu, which was higher than the required postage to East Germany (required postage 12 xu). So, the letter may have been heavier than the standard 20 grams.
Here is a late usage of the Peoples Army stamp. It was mailed in February 1970 by registered mail and via Express Mail to Theo Klewitz. The cover carries total of 8 of the stamps plus some other mixed stamps for a total postage of 150 x or 1.5 Dong. The required postage to West Germany was 50 xu plus the international registration fee of 60 xu would have moved up the postage to 1.1 Dong. So, this letter may have been heavier than the standard 20 grams.
Registration Nr. 100310