Picture postcards like this one were given out for free on the ship HQ 04, the Tuy Dong in the early 1970s. They may have been available on other ships as well.
The postcard depicts the Tuy Dong and HQ 07, the Dong Da II. It was sent by a First Lieutenant on board HQ 09, the Ky Hoa, on 26 Feb 1972 operating from KBC 6678. It is stamped with a nice HQ 09 cachet.