You show no images of the other side of the part, so it is impossible to tell. Hi-pot testing usually is between a transformer's primary and secondaries, but it could be from a single inductor to the frame.
If you are sure it a) is undamaged, and b) has no other electrical connections, then it could be a custom designed choke for an old Astec power supply. Old, because Astec's name changed to Emerson, then to Artesyn.
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