Thank you both for reply;
@4thDoctorWhoFan - Thanks, but I really don't think is a low voltage stabistor. I don't think this device would be used in PC power supply, would it? I don't know really. It near the LED side of the opto-isolator EL816, all 3 legs are used, hence I am inclined to think is the TL431 variants, not sure,. guessing.
@cvanc - Thanks for reply. Just checked and confirmed, its the lighting & shadow effect. Visually checked and continuity checked [pin and solder/track]