Wow! Antique-shop.com forums are in the big #1 spot on Google for the search term "antique shop forum", for 4 years running!Thanks to YOU.
Have you tried a magnet on them?http://www.ebay.com/itm/Vintage-Cast-Iron-Woman-Sewing-or-Playing-Piano-Bookends-Set-LOOK-/300947711063?pt=LH_DefaultDomain_0&hash=item4611e1a457