I am trying to find old newspaper articles, magazine articles, photographs and
advertisemants for Miriam Haskell jewelry from 1920 until 1970.

Grace --

You may want to get to a good research library where microfilm or
online access to old ads and articles is available.  A quick search of
the New York Times archive turns up 33 articles, photos and
advertisements for the period that you're interested in.  The New York
Times is available at many public libraries online via Proquest
Historical newspapers, a commercial database service (and some
libraries have microfilm access).

There are also other databases with popular magazines which could give
you hundreds of potential references.

Best regards,

Omnivorous-GA