Eaton Cooper Power series current limiting backup fuse, Under oil, 15.5 kV, 2.1 inch diameter, Distribution C, 165A, 50 kA max interrupt current, 400A min interrupt current, ELSP, 1/4-20 threaded hole both sides

DC fuse, EV fuse, high speed fuse, current limiting fuse cross reference.
Bussmann, Littelfuse, Mersen, ABB, Schneider, Eaton, HPS( Hammond Power Solutions), Amphenol, Molex distributor.