The postcard shows a still life painting by Greg Bolaños entitled Guyabanos. I was able to find an article about the life of the painter entitled "King of Pastel gets his due". It stated that Greg Bolaños is acknowledged as the King of Pastel. The subjects for Bolanos have also remained the still-lifes, nudes, and portraits that he’s been known for.
I couldn't find additional information about the painting nor its location (private collection or museum), but National Bookstore owner Socorro Ramos has still-life collections done by Bolaños.
Guyabano or soursop is somewhat difficult to eat, as the white interior pulp is studded with many large seeds, and pockets of soft flesh are bounded by fibrous membranes. Comparisons of its flavour range from strawberry and pineapple mixed together to sour citrus flavour notes contrasting with an underlying creamy roundness of flavour reminiscent of coconut or banana.
Manila Standard Today Article: King of Pastel gets his due
Soursop Wikipedia Entry