Back in December I posted a request for more information about a cover with a crab insignia. Here is a quick summary of what I have learned.
The cover is related to the Phoenix program. It was sent from the "Rung Chi Linh" training facility in Vung Tau built for the Binh Dinh Nong Program. Paramilitary police also trained here. "Rung Chi Linh" is printed on the inside of the letter sheet, so the crab is definitely the program's insignia.
As you can tell from some of my posts I am spending time focusing on US Forces, especially early involvement (1945-1964) and material related to covert operations - both US and Vietnamese. If you have interesting items to sell/trade, let me know.