Original sentence: While none of the major TV networks preserved much of their '50s programming, it's unclear whether DuMont themselves kept any recordings of the show, since DuMont's archive was destroyed in the '70s by an unnamed successor company
Edited sentence: While none of the major TV networks preserved much of their '50s programming, it's unclear whether DuMont themselves kept any recordings of the show, since DuMont's archive was destroyed in the '70s by METROMEDIA, the successor company