What a bummer for me that many pre 80 Vietnam are valuable now.

I used to have a nice collection. I have a Vietnamese (and also a Cambodian) sister from whom I received many stamps sent by her relatives in Vietnam. A Vietnamese co-worker back in the late 70s also gave me some stamps. I sold almost all of them for a pittance in the early 90s. I did keep a beautiful handpainted cover with a gorgeous handmade Christmas greeting card. The artistic abilities of the Vietnamese rivals that of the Chinese.
Sorry, I can't post a scan, it is stored in the US.

Marty