Means the same as the phrase, "just to be sure"; the "it's Westinghouse"
part originated from
television commercials for Westinghouse
Electric in the 1950s, who's catchphrase was, "You can be sure, if it's Westinghouse".
{
Craig}: Hey
Paul, did you remember to charge your wheelchair today?
{
Paul}: I think so but let me check just to be sure it's Westinghouse.