(Sarah of the Clue Crew reports from the Steinway & Sons factory in New York.)  Steinway stopped using this material in keys decades ago, & in 1993 the company patented a piano key material made of a substitute for it
High quality plastic replaced the 
elephant ivory,... [DOC] [TLE] Steinway & Sons Grand Piano | National Museum of American History [PAR] This piano is serial number 1199 and has a compass of AAA-a4, repetition action 
... iron (frame: material) ... Place Made: United States: New York, New York.