OK, my best guess is probably a KO-CAP polymer electrolytic capacitor from Kemet/Yageo.
It’s likely one of the following (note height difference):
- T521B156M025ATE100 “B” case 3.5L x 2.8W x 1.9H (mm)
- T527K156M025ATE150 “K” case 3.5L x 2.8W x 1.0H (mm)
From the datasheet:
