Yup, as flatgate said, the vast majority of blue NM Blackhawks have aluminum grip frames and ejector housings.
Then a few years ago, Ruger changed the ejector housing to steel on all New Model SA's that had steel grip frames...Bisleys, NM Super Blackhawks, Vaqueros...all separate variations.
A little history here for you, I think this way of thinking might have been started while Paul Lantuch was engraving SA's privately for WBR and/or the company. You will note that at least some (all?) of the SA's he did had steel ejector housings on them (check out the offset :shock: housings on the guns pictured in "Ruger & His Guns" by R. L. Wilson, pages 139 and 140!), but this got a few at the factory to start experimenting again with steel housings (and for those involved with Cowboy action shooting....even a few brass housings were made).
Chet15